PubMed Health⌕ Search

Biomedical subjects

I R Hamilton

Publications and source records attributed to I R Hamilton.

At least 55 records · Page 3Linked to original sources
PubMed1983

The influence of growth rate and nutrient limitation on the microbial composition and biochemical properties of a mixed culture of oral bacteria grown in a chemostat.

A sample of human dental plaque was homogenized in transport fluid and inoculated simultaneously into a glucose-limited and a glucose-excess chemostat maintained at pH 7.0 and a dilution rate (D) of 0.05 h-1. In an attempt to ensure the establishment of slow-growing bacterial populations, two further inoculations of each chemostat with fresh samples of dental plaque took place before a steady-state was attained at this dilution rate. The dilution rate was increased step-wise to D = 0.6 h-1, and then returned directly to D = 0.05 h-1. Contrary to chemostat theory, microbial communities with a high species diversity were maintained under all of the experimental conditions employed, although not all of the bacterial populations present in the inocula established successfully in the chemostat. At each steady-state the bacteriological composition and biochemical properties (fermentation products, enzyme assays and acid production) of the communities of each chemostat was determined. Higher cell yields and a slightly more diverse community were obtained from the glucose-limited chemostat at all dilution rates. A complex mixture of end products of metabolism was obtained from the glucose-limited chemostat, suggesting amino acid catabolism, while lactate was the predominant acid of the glucose-excess culture. In washed-cell experiments, communities from the glucose-excess chemostat produced the lower terminal pH values following a pulse of glucose, with the lowest pH values occurring at the higher dilution rates. A film of micro-organisms, which accumulated around the neck of the chemostat, was sampled at the end of the experiment. The microbial composition of the films from each chemostat differed markedly, and both were different to the community of the bulk fluid of the respective chemostat. Spirochaetes and a population of yeasts were detected in the films from the glucose-limited and glucose-excess chemostats, respectively. No invertase or glucosyltransferase activity, and little glucoamylase-specific glycogen was detected in the communities from either chemostat, although significant endogenous activity, particularly at high dilution rates, was obtained with washed-cells from the glucose-excess chemostat. The results suggest that the chemostat could make a valuable contribution to the study of the ecology of dental plaque.

Bacteria↗
PubMed1983

Carbohydrate metabolism by Actinomyces viscosus growing in continuous culture.

A human oral strain of Actinomyces viscosus, GN431/75, was grown anaerobically in a defined medium in continuous culture with a glucose limitation at dilution rates (D) between 0.025 and 0.2 h-1 and with a nitrogen limitation at D = 0.005 and 0.1 h-1. With 5 mg of glucose per ml, the culture was limited for carbon at D = 0.025 and 0.05 h-1, but became nitrogen limited (asparagine) at D = 0.1 and 0.2 h-1. The molar growth yield (Yglucose) decreased from 50.0 to 40.9 g of cells per mol of glucose as the dilution rate was increased from 0.025 to 0.2 h-1, reflecting the limitation of asparagine. With high glucose and low amino acid concentrations (nitrogen limited), the cell yields at D = 0.05 and 0.1 h-1 were 37 to 33% lower than in the glucose-limited culture. The major products of metabolism were succinic and lactic acids with lesser amounts of acetic and formic acids and ethanol. The rate of glucose fermentation by resting cells removed from the glucose-limited culture and assayed in a pH stat increased with the dilution rate and was always higher than that for the fermentation of sucrose (60%) and fructose (40%). Activity for the glucose-P-enolpyruvate phosphotransferase system was observed in whole homogenates, with the highest activity evident at D = 0.1 h-1 with the glucose-limited culture. The observed activity was significantly lower than the rate of glucose metabolism at each dilution rate, suggesting that glucose-P-enolpyruvate phosphotransferase system was underestimated or that an additional transport system exists in the organism. The glucose-limited culture showed considerable ability to synthesize glycogen during the transition from carbon to nitrogen limitation, when 35% of the cell mass was present at this polymer. The organism was shown to possess the glycogen synthetic enzymes ADP glucose synthase and ADP glucose transferase, as well as the degradative enzyme maltodextrin phosphorylase. Washed cells of A. viscosus GN431/75 were shown to be relatively insensitive to the inhibiting actions of NaF in pH-fall and constant-pH experiments at all dilution rates. At pH 7.0, 25 mM NaF was required to completely inhibit glycolysis by glucose-limited cells at D = 0.05 h-1, whereas a concentration of only 11 mM NaF was required with cells of Streptococcus mutans grown and incubated under identical conditions. An interesting feature of the growth of A. viscosus GN431/75 in the chemostat was the shift from individual nonadherent cells at the low dilution rates to the appearance at D = 0.2 h-1 of large cell aggregates forming tenacious adherent films reminiscent of its characteristics in the oral cavity.

Actinomyces↗
PubMed1982

Microbial populations growing in the presence of fluoride at low pH isolated from dental plaque of children living in an area with fluoridated water.

Longitudinal microbiological examinations have been made of dental plaque from a site approximal to the upper central incisors of 10 8-year-old children living in an area with water fluoridation. Differential counts of viable bacteria, made using a selective medium containing various levels of fluoride (0 to 100 mug/ml) at pH levels of 7.0 to 5.5, demonstrated an effect of both pH and fluoride on the numbers and types of bacteria isolated. Strains of Streptococcus and Neisseria grew after only 16 h of incubation at pH levels as low as 6.0 with fluoride levels up to 50 mug/ml. The most commonly isolated streptococci were Streptococcus mitior and S. salivarius. S. mutans was isolated less frequently and was inhibited by 20 and 50 mug of fluoride per ml at pH 6.0 and 6.5, respectively. Veillonella strains were the most resistant isolates, being isolated after 16 h of incubation on media at pH 6.0 with 100 mug of fluoride per ml. Despite their known fluoride resistance, Actinomyces spp. were often only detected on the selective media after 72 h of incubation. The pH of the medium had a definite selective effect, as the number of colonies growing on the fluoride-free basal media at pH 6.0 was only 30% of that at pH 7.0. Representative strains of S. mutans, S. mitior, S. sanguis, and S. milleri were tested for their ability to utilize glucose at the pH and fluoride levels of the medium on which they were initially isolated. Fluoride reduced the initial glycolytic rate of the cells, but in 5 of the 13 strains tested the final amount of glucose used after 2 h of incubation was the same in the presence or absence of fluoride. The isolation of bacteria capable of growth in the presence of fluoride over a significant portion of the pH range that occurs in plaque in vivo could explain in part the finding that fluoride does not have a dramatic effect on the plaque community. Fluoride in plaque may reduce the ecological advantage afforded to aciduric S. mutans strains by carbohydrate substances. In the in vivo situation this could mean that, even with high carbohydrate intake, fluoride may permit S. mitior to compete with S. mutans within the plaque ecosystem.

Actinomyces↗
PubMed1982

Response of freshly isolated strains of Streptococcus mutans and Streptococcus mitior to change in pH in the presence and absence of fluoride during growth in continuous culture.

A study was undertaken to compare the effects of pH and fluoride on the growth and metabolic properties of Streptococcus mutans 2452 and Streptococcus mitior 572, strains recently isolated from 8-year-old school children and grown in continuous culture with a glucose limitation. Each experiment had four consecutive stages of growth: (i) pH 7.0, (ii) no pH control, (iii) pH 7.0, and (iv) no pH control plus 50 mug of fluoride per ml in the medium. At a dilution rate (D) of 0.13 h (-1), cells of S. mitior possessed high glycolytic activity at pH 7.0 in the initial stage, but were washing out of the chemostat within 24 h after the pH control was shut off and the pH fell to 5.1. Once the culture was reestablished at pH 7.0, fluoride (50 mug/ml) was added to the medium and the pH control was again turned off. Whereas cell numbers fell from 24.0 x 10(8) to 0.9 x 10(8)/ml within 24 h, the culture remained relatively constant during the following 6 days despite the fall in pH to 5.4. The cells from this culture also maintained an intermediate glycolytic rate of 0.44 mumol mg(-1) min(-1). The cells in this latter stage developed phenotypic resistant to fluoride at concentrations up to 16 mM. Growth of S. mitior at D = 0.034 h(-1) resulted in a slower response to environmental change such that cells were able to grow to pH values as low as 5.2 in the absence of fluoride. In contrast to S. mitior, S. mutans 2452 under the same conditions at D = 0.13 h(-1) grew to higher cell numbers and higher yields and was able to maintain significant cell numbers to pH 4.8 once the pH control was shut off in the presence and absence of fluoride. S. mutans had 40% less glycolytic activity but was fourfold more resistant to fluoride at the start of the experiment, and cells were shown to adapt to growth at low pH and to fluoride at levels as high as 20 mM. This fluoride resistance by freshly isolated S. mutans 2452 was significantly higher than that of S. mutans DR0001 grown under identical conditions in the chemostat. S. mutans DR0001 is a strain which has been subcultured in vitro for several years. This study demonstrated that S. mutans 2452 was more aciduric than S. mitior 572 and, unlike the latter organism, could grow at pH values below 5.1. The addition of fluoride to the medium stabilized the S. mitior culture in the absence of pH control, indicating that whereas fluoride does suppress growth and glycolytic activity it also results in higher environmental pH values, which permit the survival of the less aciduric bacteria.

Culture Media↗
PubMed1982

Evidence for the involvement of proton motive force in the transport of glucose by a mutant of Streptococcus mutans strain DR0001 defective in glucose-phosphoenolpyruvate phosphotransferase activity.

Streptococcus mutans DR0001 and a glucose-phosphotransferase (PTS)-defective mutant, DR0001/6, were grown anaerobically in a chemostat with a glucose limitation at dilution rates (D) of 0.04 to 0.6 h(-1) (mean generation time, 17 to 1.2 h). The mutant possessed only 15% of glucose-PTS activity of the wild type and gave cell yields (19%) less than those of the wild type. Glucose-PTS activity in strains DR0001 was maximum at D = 0.1 h(-1) and was adequate to account for transport in the chemostat at all dilution rates except D = 0.6 h(-1), at which it was 80% of the actual glucose uptake activity. The mutant DR0001/6, on the other hand, possessed only sufficient glucose-PTS activity to sustain growth at below D = 0.1 h(-1), indicating the presence of an alternate transport activity. This was confirmed in glycolytic rate experiments with washed cells, which demonstrated that the mutant showed rates 11- to 27-fold higher than that accountable via glucose-PTS activity alone. The wild-type organism contained both a high (K(s), 6.7 to 8.0 muM)- and a low (K(s), 57 to 125 muM)-affinity transport system, whereas the glucose-PTS-defective mutant contained only the low-affinity system (K(s), 62 to 133 muM). The glucose-PTS was shown to be the high-affinity system. Glucose uptake by the mutant was unaffected by 8 mM sodium arsenate, 10 mM azide, and 10 mM dinitrophenol but was completely inhibited by 0.05 mM sodium iodoacetate. Glycolysis in the organism was almost completely inhibited by 0.25 mM N',N' -dicyclohexylcarbodiimide (DCCD), indicating the involvement of an ATPase in glucose uptake. The ionophores carbonylcyanide-m-chlorophenylhydrazone and tetrachlorosali-cylanilide were inhibitory at concentrations of 10 muM, suggesting that a proton gradient was important in the transport process. Higher levels of DCCD and the ionophores were required to inhibit the wild-type organism to the same degree. A mechanism is proposed for the alternative transport system whereby proton motive force is created by the extrusion of protons by the DCCD-sensitive ATPase and glucose is transported down a proton gradient in a symport with protons.

Adenosine Triphosphatases↗
PubMed1982

Properties of Streptococcus mutans Ingbritt growing on limiting sucrose in a chemostat: repression of the phosphoenolpyruvate phosphotransferase transport system.

Growth of Streptococcus mutans Ingbritt on limiting sucrose in a chemostat at dilution rates of 0.05 to 0.4 h-1 (mean generation time, 14 to 1.7 h) resulted in a heterofermentative pattern of metabolic end products. During fast growth, lactic acid was the major end product, whereas at slower growth rates, acetic and formic acids, as well as ethanol, increased to be major end products. The patterns obtained were similar to those seen with the same organism growing on glucose. The glycolytic rate by washed cells was maximum at the lowest dilution rates and decreased as the cells were made to grow faster. Transport of sucrose, glucose, and fructose via the phosphoenolpyruvate phosphotransferase system (PTS) was repressed during growth on sucrose after growth on glucose. Uptake rates suggested that sucrose was transported in the PTS as the intact disaccharide. Comparison of the rate of sugar uptake in the chemostat with the rate of PTS activity in the cells at each growth rate indicated that the PTS was capable of supporting growth only at a dilution rate of 0.05 h-1. Growth on sucrose at faster growth rates required the activity of a second transport system, supporting our earlier observations with glucose that S. mutans contains at least two sugar transport systems.

Biological Transport↗
PubMed1982

Properties of oxaloacetate decarboxylase from Veillonella parvula.

Oxaloacetate decarboxylase was purified to 136-fold from the oral anaerobe Veillonella parvula. The purified enzyme was substantially free of contaminating enzymes or proteins. Maximum activity of the enzyme was exhibited at pH 7.0 for both carboxylation and decarboxylation. At this pH, the Km values for oxaloacetate and Mg2+ were at 0.06 and 0.17 mM, respectively, whereas the Km values for pyruvate, CO2, and Mg2+ were 3.3, 1.74, and 1.85 mM, respectively. Hyperbolic kinetics were observed with all of the aforementioned compounds. The Keq' was 2.13 X 10(-3) mM-1 favoring the decarboxylation of oxaloacetate. In the carboxylation step, avidin, acetyl coenzyme A, biotin, and coenzyme A were not required. ADP and NADH had no effect on either the carboxylation or decarboxylation step, but ATP inhibited the carboxylation step competitively and the decarboxylation step noncompetitively. These types of inhibition fitted well with the overall lactate metabolism of the non-carbohydrate-fermenting anaerobe.

Adenosine Triphosphate↗
PubMed1982

Inorganic pyrophosphatase activity in oral streptococci: purification and properties of the enzyme from Streptococcus salivarius.

Inorganic pyrophosphatase has been purified from the soluble fraction of Streptococcus salivarius by protamine sulfate treatment, ammonium sulfate fractionation, and chromatography on Sephadex G-200 and DEAE-cellulose. The enzyme was purified approximately 500-fold with a 33% yield. The purified enzyme was homogeneous since it showed a single band when examined by nondenaturing polyacrylamide gel electrophoresis. It was rich in acidic (glutamic and aspartic) amino acids, as well as serine and glycine. The enzyme was devoid of sulfur-containing amino acids. The purified enzyme was specific for the hydrolysis of inorganic pyrophosphate and did not hydrolyze any other phosphate-ester compound examined. Inorganic pyrophosphatase activity was completely dependent on a divalent cation. Activity was maximum in the presence of Mg2+ while activity in the presence of Mn2+ and Co2+ was significantly lower. In the presence of Mg2+, a number of divalent cations, however, inhibited the enzyme activity. The true substrates for S. salivarius inorganic pyrophosphatase were magnesium-pyrophosphate complexes, i.e., MgPPi and Mg2PPi, while free Mg2+ had no effect on the enzyme activity and free PPi inhibited the hydrolysis of inorganic pyrophosphate. Km value for magnesium-pyrophosphate complexes was 16.4 microM. Km value for total Mg2+ was similar ranging between 14.4 and 20 microM. Analysis of data by Hill plots indicated one binding site for Mg2+ and two for PPi. Among various nucleotides and glycolytic intermediates examined, GDP, GMP, and fructose-1, 6-P2 showed significant inhibitory effect on enzyme activity.

Amino Acids↗
PubMed1979

Effect of growth rate and glucose concentration on the activity of the phosphoenolpyruvate phosphotransferase system in Streptococcus mutans Ingbritt grown in continuous culture.

Streptococcus mutans Ingbritt was grown anaerobically in a chemostat with a glucose limitation, as well as with an excess of glucose (amino acid limitation) at dilution rates (D) between 0.05 and 0.4 h(-1) (mean generation time = 12 to 1.5 h). The glucose-limited culture produced cells having 1.5- to 6.0-fold greater glycolytic activity than the cells from the glucose-excess culture. The preferred substrate for these cells was glucose, with the glycolytic rate for sucrose being only slightly lower; the rate for fructose was half that of glucose. The glycolytic rate of the glucose-limited cells was maximum at D = 0.1 h(-1), with a decline in rate as the growth rate approached D = 0.4 h(-1). A comparison of the activity of phosphoenolpyruvate phosphotransferase system (PTS) in the two types of cells showed that the glucose-limited cells had 1.7- to 5.6-fold greater PTS activity for the three sugars than the glucose-excess-grown cells. Whereas little difference was seen between the three sugars with the latter cells, the glucose-PTS had the greatest activity with glucose-limited cells, with the maximum in cells grown at D = 0.1 h(-1). Comparison of the rate of sugar uptake in the chemostat with the rate of PTS transport activity in the cells at each growth rate demonstrated that only under conditions of slow growth with a glucose limitation was the PTS system capable of supporting growth on glucose. Furthermore, PTS activity in cells grown with an excess of glucose was insignificant when compared with glucose uptake during growth in the chemostat. This evidence supports the observation that S. mutans possesses at least one other system, in addition to the PTS, for the transport of glucose into the cell. The organism was, however, devoid of glucose-proton symport transport activity.

Biological Transport, Active↗
PubMed1979

Effect of growth rate and glucose concentration on the biochemical properties of Streptococcus mutans Ingbritt in continuous culture.

A comparison was made of the properties of Streptococcus mutans Ingbritt grown in continuous culture under conditions of excess glucose (nitrogen limitation) and limiting glucose at mean generation times of 1.7 to 14 h. Only low levels of glucoamylase-specific glycogen were formed in cells from either culture, and the total carbohydrate content of the cells under excess glucose was only at most 1.6-fold higher than in the glucose-limited culture. A negligible amount of cell-free polysaccharide was formed in either culture, although a significant level of glucosyltransferase activity was observed in both, with the highest activity at D = 0.2 and 0.4 h(-1) with a glucose limitation. Other differences were observed. (i) Lactate was the main end product of the glucose-excess culture, whereas acetate, formate, and ethanol were the main products of the glucose-limited culture except at a mean generation time of 1.5, when lactate represented 30% of the products. (ii) The yield (in grams per mole of glucose) of the latter culture was 2.6- to 4.0- fold higher than the yield of the glucose-excess culture. (iii) Washed cells from the glucose-limited culture were much more acidogenic (1.7- to 6.2-fold) than the glucose-excess cells when incubated with glucose, sucrose, and fructose. Endogenous glycolytic activity by the latter cells was significant, being 31 to 92% of the exogenous glucose rate at the four dilution rates. (iv) Cells from the glucose-excess culture were more insensitive to fluoride than cells from the glucose-limited culture. The NaF 50% inhibition dose values for the effect of fluoride on the metabolism of glucose, sucrose, and fructose were calculated for the four dilution rates at four pH values. This analysis indicated that rapidly metabolizing cells were more sensitive to fluoride than cells that metabolized the sugars more slowly.

Acetates↗
PubMed1978

Effects of fluoride on carbohydrate metabolism by washed cells of Streptococcus mutans grown at various pH values in a chemostat.

Streptococcus mutans Ingbritt was grown anaerobically in a chemostat, at a rate (mean generation time, 13 h) similar to that in dental plaque, in a complex medium with excess glucose and at pH values of 6.5, 6.0, and 5.5. The yield of cells was constant at pH 6.5 and 6.0 (2.00 mg/ml) but fell to 1.25 at pH 5.5; Y(glucose) was relatively constant under all conditions. Lactic acid was the major end product. Amino acid analysis of the culture supernatants indicated that growth was probably limited by the availability of cysteine. Cells were harvested and monitored for their capacity to produce acid from endogenous polysaccharide and exogenous sugars in the presence and absence of NaF, as well as for their glucose phosphoenolpyruvate (PEP)-phosphotransferase activity. Surprisingly, cells grown at pH 5.5 possessed two to three times more glycolytic activity, as measured by the rate of acid production, than cells grown at pH 6.5 and 6.0 when incubated in a washed suspension at constant pH with a sugar source. Furthermore, the cells grown at pH 5.5 were about twice as resistant to the effect of NaF in reducing the rate of acid production in this system. Fluoride inhibition could be reversed by increasing the pH of the system. Cells grown at all three pH values showed significant acid production from endogenous reserves, despite the fact that the glucoamylase-specific glycogen content of the cells dropped from 33% of the total carbohydrate during pH 6.5 growth to only 3% after growth at pH 6.0 and 6.5. Incubation of washed cells for 18 h in phosphate buffer resulted in the loss of 62% of the total carbohydrate, indicating that nonglycogen cellular polysaccharide was metabolized. A comparison of the fluoride effect on endogenous and exogenous metabolism under pH fall conditions showed that, with pH 6.5- and 6.0-grown cells, the inhibitor was more effective in the presence of an exogenous carbon source than in its absence. This effect was not seen with pH 5.5-grown cells. The decreased sensitivity of the pH 5.5-grown cells to fluoride was probably associated with the decreased glucose PEP-phosphotransferase activity (11%) in these cells compared with the activity of those grown at pH 6.5. This evidence supports the hypothesis that S. mutans possesses at least two glucose transport systems, one of which is relatively fluoride insensitive.

Amino Acids↗
PubMed1978

Co-induction of beta-galactosidase and the lactose-P-enolpyruvate phosphotransferase system in Streptococcus salivarius and Streptococcus mutans.

The addition of lactose, galactose, or isopropyl-beta-D-thiogalactoside (IPTG) to glucose-grown cells of Streptococcus salivarius 25975 resulted in the co-induction of both the lactose-P-enolpyruvate phosphotransferase system (lactose-PTS) and beta-galactosidase, with the latter the predominant metabolic system. With various strains of Streptococcus mutans and Streptococcus sanguis 10556, on the other hand, the lactose-PTS was the major metabolic pathway with beta-galactosidase induced either to low or negligible levels. In all cases, induction of the lactose-PTS resulted in the concomitant induction of 6-P-beta-galactosidase. The induction by lactose of both the lactose-PTS and beta-galactosidase in all strains was repressed by glucose and other catabolites, notably, fructose. Induction of beta-galactosidase in S. salivarius 25975 by IPTG was, however, relatively resistant to glucose repression. Induction experiments with IPTG and lactose suggested that a cellular metabolite of lactose metabolism was a repressor of enzyme activity. Exogenous cAMP was shown to reverse the transient repression by glucose of beta-galactosidase induction in cells of S. salivarius 25975 receiving lactose, provided the cells were grown with small amounts of toluene to overcome the permeability barrier to this nucleotide, cAMP, was however, unable to overcome the permanent repression of beta-galactosidase activity to a significant extent under these conditions.

Cyclic AMP↗
PubMed1975

Purification and regulatory properties of pyruvate kinase from Veillonella parvula.

The nonglycolytic, anaerobic organism Veillonella parvula M4 has been shown to contain an active pyruvate kinase. The enzyme was purified 126-fold and was shown by disc-gel electrophoresis to contain only two faint contaminating bands. The purified enzyme had a pH optimum of 7.0 in the forward direction and exhibited sigmoidal kinetics at varying concentrations o-f phosphoenol pyruvate (PEP), adenosine 5'-monophosphate (AMP), and Mg-2+ ions with S0.5 values of 1.5, 2.0, and 2.4 mM, respectively. Substrate inhibition was observed above 4 m PEP. Hill plots gave slope values (n) of 4.4 (PEP), 2.8 (adenosine 5'-diphosphate), and 2.0 (Mg-2+), indicating a high degree of cooperativity. The enzyme was inhibited non-competitively by adenosine 5'-triphosphate (Ki = 3.4 mM), and this inhibition was only slightly affected by increasing concentration of Mg-2+ ions to 30 mM. Competitive inhibition was observed with 3-phosphoglycerate, malate, and 2,3-diphosphoglycerate but only at higher inhibitor concentrations. The enzyme was activated by glucose-6-phosphate (P), fructose-6-P, fructose-1,6-diphosphate (P2), dihydroxyacetone-P, and AMP; the Hill coefficients were 2.2, 1.8, 1.5, 2.1, and 2.0, respectively. The presence of each these metabolites caused substrate velocity curves to change from sigmoidal to hyperbolic curves, and each was accompanied by an increase in the maximum activity, e.g., AMP greater than fructose-1,6-P2 greater than dihydroxyacetone-P greater than glucose-6-P greater than fructose-6-P. The activation constants for fructose-1,6-P2, AMP, and glucose-6-P were 0.3, 1.1, and 5.3 mM, respectively. The effect of 5 mM fructose-1,6-P2 was significantly different from the other compounds in that this metabolite was inhibitory between 1.2 and 3 mM PEP. Above this concentration, fructose-1,6-P2 activated the enzyme and abolished substrate inhibition by PEP. The enzyme was not affected by glucose, glyceraldehyde-3-P, 2-phosphoglycerate, lactate, malate, fumerate, succinate, and cyclic AMP. The results suggest that the pyruvate kinase from V. parvula M4 plays a central role in the control of gluconeogenesis in this organism by regulating the concentration of PEP.

Adenosine Monophosphate↗