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W Babel

Publications and source records attributed to W Babel.

At least 55 records · Page 3Linked to original sources
PubMed1990

The growth rate-limiting reaction in methanol-assimilating yeasts.

The maximum growth rate of methylotrophic yeasts during growth on methanol is about 0.2 h-1. Since they are able to grow faster on substrates such as glucose we tried to identify the putative limiting step in methanol metabolism within the assimilatory pathway, leading to the formation of a major precursor for biosyntheses, or within the linear dissimilatory sequence. Growth experiments with mixed substrates and determination of some kinetic parameters allowed us to restrict the number of possible pacemaker enzymes. The dissimilatory sequence does not seem to be growth-rate limiting. This also applies to transketolase, transaldolase and fructose-1,6-bisphosphatase. Surprisingly, methanol oxidase appears to be the prime candidate.

Alcohol Oxidoreductases↗
PubMed1989

[Preparation of preoral sustained-release preparations with a base of biodegradable polymers. 3. Preparation of matrix tablets with a base of poly-3-hydroxybutyric acid].

Poly-3-hydroxybutyric acid belongs to the biological polymers, which are produced by bacterials. The determination of the grain size, moisture content, flowability and the parameters for the direct compression was performed in regard of their use as auxillary substance for the preparation of solid sustained release dosage forms. The production of the matrix tablets was performed on the basis of a factorial design. The content of substance, an addition of Heweten 12 and the compression power served as factors. Caffeine was used as model drug. The in vitro release values show, that all three factors have an influence of the drug release. Optimized matrix tablets were produced on the basis of this result.

Chemistry, Pharmaceutical↗
PubMed1989

Detoxification of formaldehyde by acetic acid bacteria.

Formaldehyde resistance of methylotrophic and non-methylotrophic Acetobacter strains was investigated. A facultatively methylotrophic Acetobacter methanolicus (MB58) gets rid of free formaldehyde by assimilating it. Heterotrophically growing cells tolerate 12 mM free formaldehyde. Non-methylotrophic but methanol oxidizing Acetobacter pasteurianus strains possess the same level of formaldehyde resistance. Formaldehyde resistance can be drastically lowered down to 4 mM by blocking the formate dehydrogenase by means of hypophosphite. Acetobacter spp. Martin 1 and LMG 76.10 are not able to oxidize methanol or formaldehyde via formate to CO2 and possess a significantly lower formaldehyde resistance (4 mM). Hence high formaldehyde resistance of the Acetobacter spp. investigated is based above all on a properly operating linear dissimilatory sequence. The dissimilatory RuMP cycle can hardly help detoxify formaldehyde.

Acetobacter↗
PubMed1987

Completion of the amino acid sequence of the alpha 1 chain of human basement membrane collagen (type IV) reveals 21 non-triplet interruptions located within the collagenous domain.

The cDNA and protein sequences of the N-terminal half of human basement membrane collagen (type IV) have been determined. Overlapping cDNA clones were constructed by repeated primer extension with synthetic oligonucleotides. They cover 2953 bp, beginning at the 5' end of the corresponding mRNA. At the protein level, the sequence of the cyanogen bromide peptide CB6 adjacent to the 7S domain has been additionally elucidated. The data presented here complete the protein sequence and nearly the entire cDNA sequence of the human alpha 1(IV) chain. The amino-terminal half of the alpha 1(IV) chain contains 8 cysteine residues involved in intramolecular and intermolecular cross-links. The entire triple-helical domain of alpha 1(IV) is interrupted by 21 non-triplet regions.

Amino Acid Sequence↗
PubMed1985

[Acetobacter methanolicus--a new organism for genetic studies].

A new bacterial strain is described belonging to Acetobacter methanolicus species. It is of industrial value as a producer of protein and methanol products. The strain is acidophile and this feature comprises a conspicuous technological advantage. The results of bacteriophage and cell interactions are reported. They might be potentially useful for elaboration of the transduction technique for the strain. The collection of mutants was obtained including those utilizing methanol, having auxotrophic markers as well as streptomycin and rifampicin resistances. The transfer of plasmids RSF1010 and R68 to Acetobacter methanolicus from other bacteria has been demonstrated.

Acetobacter↗
PubMed1984

Structure of human-basement-membrane (type IV) collagen. Complete amino-acid sequence of a 914-residue-long pepsin fragment from the alpha 1(IV) chain.

The complete amino acid sequence of the 914-residue-long pepsin fragment alpha 1 (IV)95 from the alpha 1 chain of human placental basement membrane (type IV) collagen is presented. This sequence contains 12 interruptions of the collagenous triplet sequence Gly-Xaa-Yaa which varied in length from 1 to 11 residues. The distribution of amino acids between the Xaa and Yaa position was similar to that found in interstitial collagens but the extent of proline and lysine hydroxylation differed. Computer comparisons of the alpha 1 (IV)95 sequence with those of the interstitial collagen chains did not reveal any homology, whereas a comparison with the partial sequences of mouse tumor and bovine lens capsule alpha 1 (IV) showed an approximately 85% identity. The unique sequence characteristics of type IV collagen are discussed in relation to its macromolecular structure and to the interstitial collagens.

Amino Acid Sequence↗
PubMed1983

The binding of bongkrekate to mitochondria.

The binding of bongkrekate to mitochondrial membrane was investigated using [3H]bongkrekate. These measurements were designed to examine the previously derived reorienting site mechanism which implies that bongkrekate binds to the single carrier site only from the inner face of the mitochondrial membrane. The binding studies confirm pH-dependent accumulation of [3H]bongkrekate inside the mitochondria which superimposes on to binding of carrier sites. By breaking the membrane with Lubrol or sonication, binding to the carrier sites can be titrated and Kd approximately equal to 5 X 10(-8) M is determined. ADP or ATP increases the amount of binding but does not change the Kd. Reciprocally bongkrekate increases ADP binding in those sections of a titration curve where bongkrekate binding is increased by ADP. [35S]Atractylate is displaced by [3H]bongkrekate at a 1:1 molar ratio. This displacement is dependent on ADP concentration with the Km = 0.5 X 10(-6) M. The earlier described isomer, isobongkrekate, also binds specifically to the carrier sites. From competition with bongkrekate a ratio KisoBKAd/KBKAd = 0.10 is determined. [35S]Carboxyatractylate displaces most of [3H]isobongkrekate but only little of [3H]bongkrekate. The rate of displacement is more than 10-times faster for isobongkrekate than for bongkrekate. The displacement is dependent on ADP with a Km = 5 X 10(-6) M. All these results are fully consistent with the single site reorienting mechanism. In no instant do bongkrekate and atractylate as well as ADP or ATP bind simultaneously to the carrier.

Adenosine Diphosphate↗
PubMed1983

[Regulation of citrate synthase in facultative methylotrophic bacteria].

Commonly the TCA cycle fulfils an anabolic and a catabolic function in case of aerobic chemoorganoheterotrophic nutrition. In methylotrophic growth the TCA cycle is dispensable as a bioenergetic pathway. This is reflected by properties of citrate synthase in facultative methylotrophic bacteria. Two citrate synthases, a "chemoorganoheterotrophic" one, which is inhibited by NADH (or ATP in Acetobacter MB 58), and a "methylotrophic" one, which is not or less affected by energy indicators, were found in Pseudomonas oleovorans, Pseudomonas MS, Pseudomonas MA, and Acetobacter MB 58. The concentration of these citrate synthases depends on the manner of nutrition. Bacteria with ICL-negative-variant of the serine pathway and with ribulosebisphosphate pathway seem to possess only a "chemoorganoheterotrophic" citrate synthase. Possibly the anabolic function of this citrate synthase can be realized by metabolites.

Acetobacter↗
PubMed1983

[Improvement of Y-values of Hansenula polymorpha growth on methanol by simultaneous utilization of glucose].

The simultaneous utilization of methanol and glucose by Hansenula polymorpha MH20 was investigated in chemostat (C-limited) cultivation. The mixed-substrate utilization results in biomass yields which are greater up to 20 to 25% as expected assuming an additive growth on both substrates. This is referred to as an auxiliary-substrate effect. Additionally, methanol can be utilized at higher growth rates in the presence of glucose compared to those obtained on this substrate alone. The extend of the auxiliary-substrate effect and the optimum ratio of substrates to reach this effect depend on dilution rate. The greatest stimulation in yield is obtained at D approximately 0.1 h-1, after raising the dilution rate this effect diminishes. At a rate of 0.1 h-1 the optimum mixed-substrate ratio of methanol: glucose is 7:1 (g). By increasing the growth rate the ratio changes toward glucose and reached a value of 1:1 (g) at D = 0.3 h-1. This change in the optimum ratio correlates with diminution in yield coefficient of methanol accompanying an increase in growth rate greater than 0.15 h-1. Energy balances of the utilization of the single substrates are used for interpretation of these results. From this it is evident that methanol does not play the role of an energy-rich substrate in the metabolism of yeast. Rather glucose is the energy-providing substrate in this combination.

Ascomycota↗
PubMed1982

[Cytochrome pattern of methylotropic acetic acid bacterium MB 58 as dependent on growth conditions].

In contrast to methylotrophic bacteria investigated up to now the facultative methylotrophic Bacterium MB 58 (Acetobactersp. MB 58) does not possess a cytochrome aa3-complex, but we could find out cytochrome, cytochrome cco, cytochrome a1, and moreover cytochrome d in dependence on the growth conditions. Cytochrome d was found only in stationary phase of heterotrophic growth. Under methylotrophic growth conditions cytochrome d could be demonstrated only by lowering of the aeration rate during the fermentation, by variation the pH-value of the growth medium from 4.0 to 6.5 and with low growth rates (low dilution rates) during continuous fermentation. The addition of cyanide to the oxidized suspension of bacteria during the registration of the cytochrome-redox-difference spectrum allowed the selective representation of cytochrome d under all conditions even if no identification was possible in the spectrum normally. The oxidation of cytochrome d of Acetobacter sp. MB 58 in the presence of cyanide is an indication of its cyanide insensitivity. The low level of b-type cytochromes could be represented by a special technique for registration of spectra. In this connection a unknown absorption peak at 570 nm was registered. The cyanide insensitivity of cytochrome d from Acetobacter sp. MB 58 and the occurrence of several terminal oxidases is appreciated as a hint for a branched respiratory chain.

Acetobacter↗
PubMed1982

[Regulation of PEP-carboxylase of the facultative methylotrop Acetobacter sp. MB 58].

Acetobacter sp. MB 58 assimilates methanol via the fructose-1,6-bisphosphate variant of the hexulose phosphate pathway. Glyceraldehyde-3-phosphate originates as net product of an assimilation loop involving the regeneration of the C1-acceptor ribulose-5-phosphate and must be available for the de novo synthesis of the C1-acceptor as well as for the oxidative glycolysis. It is made probable in a regulatory model that this is accomplished via alternating anabolic and catabolic phases which are controlled by concerted action of PEP-carboxylase and pyruvate kinase. Whereas Ac-CoA is a crucial effector and alpha-ketoglutarate and aspartate are inhibitors for the PEP-carboxylase, the pyruvate kinase is assumed to be regulated by energy charge.

Acetobacter↗
PubMed1981

Amino acid sequence determination of the ADP,ATP carrier from beef heart mitochondria. The sequence of the C-terminal acidolytic fragment.

The primary structure of the C-terminal region (94 residues) of the ADP,ATP carrier of beef heart mitochondria is described. CNBr cleavage results in a large peptide (CB1) with Mr 22 000 and several small peptides (CB2 to CB8). Peptide separation was achieved by gel chromatography with 80% formic acid or with an ethanol/formic acid mixture. The amino acid sequence of the small CNBr peptides was determined by solid-phase techniques. Hydrolysis in formic acid cleaves the carrier protein into an Mr 23 000 fragment (A1) with the blocked N-terminus and an Mr 10 000 fragment (A2) starting with proline. The alignment of two CNBr fragments was possible by degradation of A2 by solid-phase methods for 34 steps. The remaining CNBr fragments were arranged by sequencing the tryptic peptides of citraconylated A2.

Amino Acid Sequence↗
PubMed1981

Dihydroxyacetone kinase of methanol-assimilating yeasts. II. Partial purification and some properties of dihydroxyacetone kinase from Candida methylica.

Dihydroxyacetone kinase (DHAK) from the cell-free extract of methanol-grown Candida methylica was partially purified about 100-fold by a procedure employing streptomycin sulfate fractionation, ammonium sulfate fractionation, negative absorption on Cibacron blue F3G-A sephadex G 200 and DEAE-cellulose column chromatography. The enzyme was stable in 50 mM Tris-HCl buffer pH 7.5 containing 60% glycerol at -18 degrees C. The pH optimum for the activity of DHAK from C. methylica was 7.5. The purified enzyme phosphorylated dihydroxyacetone four times faster than D,L-glyceraldehyde. The apparent MICHAELIS-MENTEN constants for dihydroxyacetone and D,L-glyceraldehyde were 0.011 mM and 0.024 mM. Other C3 compounds including glycerol were not phosphorylated. ITP and UTP were used as phosphate donors with a reaction rate of 11% and 3.1%, respectively, in relation to ATP, whereas the reaction rates of DHAK from C. methylica with CTP or GTP were much lower than 1%. The reaction of DHAK depends upon the presence of divalent cations in the assay. The highest activity was found with Mg2+ ions. The reaction rates with Co2+ or Ca2+ ions were only 57.3% and 30.3%, respectively, in relation to the assay with magnesium ions. Manganese chloride in the assay led to a complete loss of activity.

Candida↗
PubMed1981

Multiplicity of 3-hexulosephosphate synthase from bacterium MB 58. 1. Product-induced transition in velocity.

Purified 3-hexulosephosphate synthase (HPS) from the facultative methylotrophic Bacterium MB 58 exhibits a burst-like progress curve. The transition appears in an abrupt manner at physiological substrate concentrations. The following phase of lower activity again shows linear progress in the observation period. Effects of substrates, temperature or dilution on the enzyme can be ruled out as causes of this transition. However, it is obvious that it takes place after the same amount of product has accumulated. That the reaction product causes this diminution in velocity can be demonstrated by varying the enzyme concentration or the possibility for accumulating product or the product concentration itself. The substrates of HPS counteract this product-induced transition in that an increased amount of the former makes necessary an increased amount of the latter to trigger the transition. The shape of the progress curve and experiments with different amounts of in situ-generated or synthesized product show that no simple product inhibition is involved. For the explanation of all phenomena observed three enzyme forms showing different affinities for substrates and product are postulated. These forms may be interconverted into each other by substrates and product of HPS in a specific manner.

Aldehyde-Lyases↗
PubMed1981

Multiplicity of 3-hexulosephosphate synthase from bacterium MB 58. 2. Generation of complex kinetic characteristics.

3-hexulosephosphate synthase (HPS) from the facultative methanol-utilizing Bacterium MB 58 exhibits a complex kinetic behaviour characterized by intermediary plateau regions. This feature could be related to the existence of multiple enzyme forms. With the aid of gel chromatography or isoelectric focusing purified HPS has partially been separated into at least four fractions. The individual enzyme forms are characterized by different kinetic properties exhibiting either hyperbolic or sigmoidal response to substrate saturation. In the sum of their action these forms generate the complex shape of the kinetic characteristics. Furthermore, these forms were found to be interconvertible. After partial separation a new equilibrium between the conformers is established in each case. The multiplicity of HPS can be demonstrated in qualitatively the same manner with the purified enzyme and with freshly prepared crude extracts. Proteolytic modifications on the enzyme as a cause for the multiplicity could be ruled out. The multiple character of the enzyme is also evident at different pH-values showing two optima. At different temperatures, anomalies in the Arrhenius plot depending on the substrate concentration were observed. From the present data a qualitative model of regulating HPS in the methylotrophic metabolism is proposed. Accordingly, several stable states of the metabolism should be realized.

Aldehyde-Lyases↗