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At least 19 recordsLinked to original sources
PubMed1976

Degradation of blood group antigens in human colon ecosystems. I. In vitro production of ABH blood group-degrading enzymes by enteric bacteria.

Human feces contain enzymes produced by enteric bacteria that degrade the A, B, and H blood group antigens of gut mucin glycoproteins. We have studied their production in fecal cultures to determine if such cultures can be a source for enzyme purification and to explore how blood group antigen-degrading enzymes are adapted in individual human colon ecosystems. They were present in fecal cultures from each of 27 healthy subjects, including ABH nonsecretors. Heat-sensitive obligate anaerobes are their major source. From 39 to 85% of the total enzyme activity produced by growing cultures was extracellular. Commercial hog gastric mucin and salivary glycoproteins, including Lea saliva which lacks A, B, and H antigens, enhance production of A-, B-, and H-degrading activity in anaerobic fecal cultures irrespective of the glycoprotein's blood group specificity. There is evidence that the host's ABO blood type and secretor status affects the specificity of blood group-degrading enzymes produced by his fecal bacteria in vitro. Thus, fecal inocula from B secretors incubated with hog gastric mucin (A and H specificity) or with Lea saliva produced greater levels of B-degrading than A- or H-degrading activity, and inocula from A secretors in similar media produced greater levels of A-degrading than B- or H-degrading activity. Blood group-degrading enzymes produced in fecal cultures are glycosidases and not proteases. The B-degrading enzyme cleaves the B antigenic determinant alpha-D-galactose from the oligosaccharide side chains of mucin glycoproteins with B specificity. Anaerobic fecal cultures containing blood group substances are a feasible source for purifying blood group antigen-degrading enzymes. Prior adaptation to blood group antigens in the gut mucins of type A and type B secretors affects the specificity of the enzymes produced in vitro.

ABO Blood-Group System↗
PubMed1976

Autoregulatory system of insulin degradation in liver. II. Relationship between blood insulin levels and GSH-dependent insulin degrading activity in liver and blood.

An autoregulatory system of insulin degradation in the liver in which the rate of insulin metabolism changes in response to fluctuation in its blood levels, was investigated. In the plasma of rats and man in the absence of reduced glutathione (GSH), insulin degradation was not observed, but when a sufficient amount of reduced glutathione was added, the plasma did degrade insulin. This GSH-dependent insulin degrading activity in plasma was quite similar to that in liver in its nature. In rats, this GSH-dependent insulin degrading activity in the liver and plasma was fluctuated in response to fluctuation in the blood insulin levels, and the GSH-dependent insulin degrading activity in plasma was well correlated with that in the liver. Similarly, in man the GSH-dependent insulin degrading activity in plasma was changed in response to fluctuation in the blood insulin levels. In plasma under the physiologic conditions, there is an insufficient amount of reduced glutathione to elicit the insulin degrading activity, but in the liver there is a sufficient amount of reduced glutathione to manifest this activity. This evidence further supports the concept that an autoregulatory system of insulin degradation in the liver exists in man.

Animals↗
PubMed2026

Biotic and abiotic degradation of PHAs: mechanisms, environments, and potential applications of degradation products.

This review seeks to compile Polyhydroxyalkanoates (PHAs) degradation studies published over the past 20 years. It highlights the effect of physical properties, such as crystallinity and molecular weight, on the decomposition rate of these molecules. Both biotic processes, mediated by bacteria, fungi, and enzymes, as well as abiotic processes, such as hydrolysis and thermal degradation, are analyzed. A repertoire of diverse microorganisms, including their metabolic pathways and enzymes for PHA breakdown, is presented. Furthermore, this review presents the decomposition of PHAs in various environments, such as soil and seawater, highlighting their potential as a sustainable alternative. Finally, the resulting degradation products are described, emphasizing their potential applications in medicine and industry. Although degradation of PHAs has been extensively studied through these years, several knowledge gaps remain undisclosed, including the degradation of diverse polyester monomers. PHAs comprise numerous monomer compositions with variable properties, which present opportunities for different applications but pose a challenge in their degradation. The reader of this review can extract useful information for both the production of PHAs and their potential applications.

Biodegradation↗
PubMed1976

Degradation of cartilage proteoglycan by human leukocyte granule neutral proteases--a model of joint injury. II. Degradation of isolated bovine nasal cartilage proteoglycan.

Extracts of human peripheral blood polymorphonuclear leukocyte granules, and two purified proteases derived from such extracts, an elastase and a chymotrypsin-like enzyme, degrade isolated bovine nasal cartilage proteoglycan at neutral pH. Viscosity studies indicate that the leukocyte granule extracts lack hyaluronidase activity and that their degradative effect on proteoglycan at physiological pH is due entirely to proteolytic action. Sepharose 4B gel chromatography and SDS-polyacrylamide gel electrophoresis of proteoglycan fractions treated with leukocyte granule enzymes at pH 7.0 indicate that they degrade one of the proteoglycan link proteins, release a fragment from the hyaluronic acid-binding portion of the proteoglycan subunit core protein, and break down the remainder of the proteoglycan subunit molecule into peptide fragments with varying numbers of chondroitin sulfate chains. Immunodiffusion studies indicate that the antigenic determinants of the proteoglycan subunit core protein and the link proteins survive treatment with granule proteases. Similar degradation of human articular cartilage proteoglycan by granule neutral proteases can be presumed to occur, in view of the similarity of structure of human articular and bovine nasal cartilage proteoglycans. The release of granule enzymes in the course of neutrophil-mediated inflammation can thus result in the degradation of cartilage matrix proteoglycan, leading to cartilage destruction and joint injury.

Animals↗
PubMed2025

Effects of a novel Paraburkholderia phage IPK on the phenanthrene degradation efficiency of the PAH-degrading strain Paraburkholderia caledonica Bk.

Phages are a major cause of bacterial mortality, affecting bacterial diversity and ecosystem functioning. However, the impact of phage-host interactions in contaminated environments and their role in pollutant biodegradation have largely been overlooked. We isolated and characterized a novel phage that infects the PAH-degrading bacterium Paraburkholderia caledonica Bk from a polycyclic aromatic hydrocarbon (PAH)-contaminated soil and investigated the effect of different multiplicity of infection (MOI) ratios on the degradation efficiency of phenanthrene. The phage IPK is a temperate phage with a wide pH and temperature tolerance and a burst size of 80  PFU ml⁻1. The phage was classified as a member of the Caudoviricetes and is related to Pseudomonas and Burkholderia phages. However, its low intergenomic similarity indicates that it is a new species. Three auxiliary metabolic genes (AMGs) related to amino acid metabolism and to bacterial growth regulation were identified in the phage genome. The highest multiplicity of infection (MOI 10) showed a rapid recovery of the host density and greater phenanthrene degradation than MOIs ranging from 0.01 to 1. This work highlights the important role of phage-host interactions in modulating the efficiency of pollutant degradation, which could be a key for improving the establishment of inoculants in bioremediation processes.

Phenanthrenes↗
PubMed2025

The mhqPOD gene cluster in lignin-degrading Paenibacillus sp. B2 encodes a pathway for the degradation of lignin-derived 5,5'-di(dehydrovanillic acid) (DDVA).

Lignin-degrading bacteria Paenibacillus sp. B2, Agrobacterium sp. B1, and Ochrobactrum sp. each contain mhqO genes encoding ring cleavage dioxygenase enzymes whose biochemical function is unknown. Each of these strains was found to degrade the biphenyl-containing lignin fragment 5,5'-di(dehydrovanillic acid) (DDVA) on solid media. An operon of five mhq genes in Paenibacillus sp. B2 was analysed via gene expression using quantitative PCR, and all five genes were highly induced (400-1000-fold overexpression) by the presence of DDVA. Recombinant azoreductase MhqP was found to demethylate DDVA to its monodemethylated derivative. Hence, these genes are proposed to be responsible for DDVA degradation, via a pathway involving the same biochemical steps as that studied in Sphingobium lignivorans SYK-6, but using several unrelated genes. Decarboxylation of later pathway intermediate 5-carboxyvanillic acid in Paenibacillus sp. B2 is proposed to be catalysed by decarboxylase UbiD, whose gene is also upregulated in the presence of DDVA. Degradation of the other fragment 4-carboxy-2-hydroxypentadienoic acid is proposed to occur via hydratase UxuA, whose gene is also upregulated by DDVA, and 4-hydroxy-4-methyl-2-oxoglutarate aldolase.

Paenibacillus↗
PubMed1977

[Isolation and characterization of Proteus mirabilis mutants deficient in DNA degradation: function of endonuclease I in postmortem DNA degradation].

DNase deficient mutants of Proteus mirabilis selected for reduced toluene induced DNA degradation were isolated. Their defect in DNA degradation was shown not only after treatment by toluene but also in crude extracts after cell disintegration by ultrasonic and in untreated starved cultures. The degradation mutants behave just as the wild type with respect ot their in vivo functions proffed. The results inidcate that the affected DNase does not have an essential function in vivo but acts in postmortem DNA degradation. Probably the DNase in question concerns the endonuclease I of P. mirabilis described by Goebel and Helinski (1971 a, b).

Cell-Free System↗
PubMed1976

Starch degradation by the mould Trichoderma viride. I. The mechanism of starch degradation.

The mechanism of starch degradation by the fungus Trichoderma viride was studied in strain CBS 354.44, which utilizes glucose, starch and dextrins but is unable to assimilate maltose. It was shown that the amylolytic enzyme system is completely extracellular, equally well induced by starch, amylose or amylopectin and that it consists mainly of enzymes of the glucoamylase type which yield glucose as the main product of starch hydrolysis. Small amounts of alpha-amylase are produced also. The enzymes produced in starch cultures degrade starch, amylose and amylopectin equally well. Enzyme synthesis in starch media takes place to a considerable extent after exhaustion of the carbon source when maximum growth has been attained. Low-molecular dextrins are degraded by extracellular enzymes of the glucoamylase type. These enzymes are produced in media containing starch or dextrins. Maltotriose is consumed for only one third leaving maltose in the culture filtrate. Maltose is hardly attacked and hardly induces any amylolytic enzyme activity. No stable alpha-glucosidase appears to be produced.

Amylases↗
PubMed1976

Kinetics and mechanism of degradation of some 5-allylbarbituric acid derivatives. Part 3: Kinetics of solvolysis of major intermediates of 5.5-diallylbarbituric acid degradation.

Solvolysis of N-diallylacetylurea and 5.5-diallylmalonuric acid was investigated in the pH range ca. 8--12 by means of spectrophotometric and t.l.c. methods. Their log k--pH profiles were constructed from the experimental results obtained by degradation at 70 degrees C. Therefore, specific catalytic rate constants and pKa's were derived. The kinetic mechanism of N-diallylacetylurea solvolysis, resulting among other things from the so-called kinetic salt effect, depends on hydroxyl-ion attack on its undissociated and monoanionic forms. However, the degradation of alpha.alpha-diallylmalonuric acid in the pH range 10--12 is an example of specific base catalysis which can be explained by hydroxyl-ion attack on its monoanionic species. The degradation of alpha.alpha-diallylmalonuric acid below pH=10 does not follow a theoretical equation postulated, because the spectrophotometric method does not allow monitoring the formation of N-diallylacetylurea in the presence of the above acid. Thin-layer chromatography was used to check different pathways of transformations of the intermediate studies.

Allyl Compounds↗
PubMedDate not supplied

[Degradation of antipyrin by pyrazon-degrading bacteria (author's transl)].

Bacteria with the ability to grow on pyrazon as sole source of carbon were isolated from soil. They also are able to grow on antipyrin. Then three metabolites of antipyrin can be isolated from the culture fluid which were identified as 2,3-dimethyl-1-(cis-2,3-dihydro-2,3-dihydroxy-4,6-cyclohexadiene-1-yl)-pyrazolone (5) (I), as 2,3-dimethyl-1-(2,3-dihydroxyphenyl)-pyrazolone (5) (II) and as 2,3-dimethyl-pyrazolone (5) (III), respectively. Compound I and II were used as substrates for enzyme studies. A dioxygenase catalyzes the enzymatic conversion of antipyrin into compound I. In the presence of NAD as cosubstrate compound I is transformed into compound II by a dehydrogenase. A pure preparation of metapyrocatechase from pyrazon-degrading bacteria converts compound II into the dephenylated heterocyclic moiety of antipyrin (III) and into 2-pyrone-6-carboxylic acid. Based on the results of the enzymatic studies a pathway for the degradation of antipyrin is proposed.

Antipyrine↗
PubMed1978

Degradation of human fibrinogen by plasmin: isolation and partial characterization of an early degradation product.

The incubation of human fibrinogen with plasmin gives rise to an early degradation product with a molecular weight of 63,000, calculated by polyacrylamide-gel electrophoresis sodium dodecyl sulfate (PAGE-SDS); this product is resistant to the action of the plasmin for short incubation times and represents 1 +/- 0.2% of the original quantity of fibrinogen. The fragment was isolated from the incubated mixture by gel filtration and has a no-identity reaction with fibrinogen fragment D against fibrinogen fragments D antiserum. The reduction gives rise to three polypeptidic chains with molecular weights of 36,000, 17,000 and 10,000 (calculated by PAGE-SDS). Study of the carbohydrate content of these polypeptidic chains from the reduced 63,000 MW fragment indicates that there is only one electrophoretic region which contains periodic acid-Schiff (PAS) positive material. As the 63,000 MW fragment has a reaction against fibrinogen fragment D antiserum and also contains PAS positive material, according to Pepper and co-workers, it can be taken to arise from the HOOC-terminal region of fibrinogen.

Chromatography, Gel↗
PubMed1976

Retention and degradation of 125I-insulin by perfused livers from diabetic rats.

The retention of degradation of insulin by isolated perfused liver have been examined. Noncyclically perfused livers from streptozotocin-diabetic rats retained 25% and degraded 10% of 125I-insulin administered as a 1-min pulse. On gel filtration (Sephadex G50F), the degradation products released into the vascular effluent eluted in the salt peak. During the 45-min interval after the end of the 125I-insulin infusion, 0.19% of the total dose was excreted in the bile. 60-90% of this material consisted of iodinated, low-molecular-weight degradation products. Inclusion of native insulin with the 125I-insulin in the pulse depressed both the retention and degradation of iodinated material; however, this reflected increased retention and degradation of the total insulin dose (125I-insulin plus native hormone). The log of the total amounts of insulin retained and degraded were linearly related to the log of the total amount of insulin infused at concentrations between 12.7 nM and 2.84 muM. Increasing the amount of native insulin in the infused pulse also depressed the total amount of iodinated material found in the bile and led to the appearance in the bile of intermediate-sized degradation products that did not simultaneously appear in the vascular effluent. Addition of high concentrations of glucagon to the infused 125I-insulin had no effect on the retention or degradation of the labeled hormone, or on the apparent size and amount of iodinated degradation products found in the vascular effluent or in the bile. Preinfusion of concanavalin A inhibited both 125I-insulin retention and degradation. A greater depression by concanavalin A of degradation than binding was also observed with isolated hepatocytes. In contrast to 125I-insulin, the retention and degradation of two iodinated insulin analogues of relative low biological potency, proinsulin and desalanyl-desasparaginyl insulin, were small. The amount of radioactivity appearing in the bile after infusion of these analogues was almost negligible. However, degradation products of these analogues that appeared in the bile and in the vascular effluent was qualitatively similar to those found after the infusion of 125I-insulin. Our findings suggest that the rapid initial uptake of 125I-insulin after its infusion into noncyclically perfused liver, as well as its subsequent degradation, behaves in a qualitatively similar fashion to the binding of 125I-insulin and its degradation by isolated rat hepatocytes. This uptake and the subsequent phase of degradation may be attributable to binding of insulin at specific recognition sites, preliminary to its transfer to a degradative site(s) presumed to be located inside the cell.

Animals↗
PubMed1976

Insulin and glucagon degradation by the kidney. I. Subcellular distribution under different assay condition.

Insulin and glucagon degradation by rat kidney homogenates and subcellular fractions was examined under a variety of conditions including high and low substrate concentrations, at pH 4 and pH 7, with and without glutathione. At high insulin concentration (4.1 - 10(-5) M) insulin degradation by the homogenate was greatest at pH 4 but at low insulin concentration (1 - 10(-10) M) insulin degradation was greatest at pH 7. At either high or low glucagon concentration glucagon degradation by the homogenate was greatest at pH 7. Glutathione at pH 7 stimulated insulin degradation at high insulin concentrations and inhibited insulin degradation at low concentrations; Glucagon degradation at pH 7 was inhibited at both high and low concentrations of glucagon by glutathionemseparation of kidney into cortex and medulla prior to homogenation produced a pattern of insulin and glucagon degradation identical to the whole homogenate but glucagon degradation by the medulla was greater than by the cortex. Examination of degradation by subcellular fractions revealed that at high concentration at neutral pH most insulin was degraded by the 100 000 X g pellet but at low insulin concentrations over 90% of the activity was in the 100 000 X g supernatant; At pH 7, at both high and low concentrations, most glucagon-degrading activity was in the 100 000 X g pellet, although the cytosol also had activity; At pH 4 most degradation occurred in the lysosomal fractions. Separation into cortex and medulla again showed similar distribution of activity as the whole gland with the medulla having more glucagon-degrading activity than the cortex. With low insulin concentrations the cortex 100 000 X g supernatant had higher relative specific activities than the medulla supernatant. Examination of recoveries of enzyme activity revealed that the subcellular fractions consistently had markedly less insulin-degrading activity than the original homogenate. This loss of activity was only discernible when insulin degradation was performed at pH 7 at low substrate concentrations. Comparable losses of glucagon-degrading activity were not seen.

Animals↗
PubMed1976

Insulin and glucagon degradation by the kidney. II. Characterization of the mechanisms at neutral pH.

Examination of insulin and glucagon degradation by rat kidney subcellular fractions revealed that most degrading activity was localized to the 100 000 X g pellet and 100 000 X g supernatant fractions. Further characterization of the degrading activities of the 100 000 X g pellet and supernatant suggested that three types of enzymatic activity were present at neutral pH. From the cytosol an enzyme with characteristics of the insulin glucagon protease of skeletal muscle was purified. This enzyme appeared to be responsible for insulin degradation by the kidney at physiological insulin concentrations. This enzyme also contributed to glucagon degradation but was not the most active mechanism for this. In the 100 000 X g pellet at least two separate enzymatic activities were present. One of these had properties consistent with those described for glutathione insulin transhydrogenase and appeared to be responsible for insulin degradation at high insulin concentration. The other enzyme was associated with the brush border and had properties consistent with the brush border neutral protease. This enzyme appeared responsible for glucagon degradation at both low and high substrate concentrations. An apparent marked synergism between the 100 000 X g pellet and the 100 000 X g supernatant was noted for insulin degradation at physiological insulin concentrations. Pellet glucagon-degrading activity and soluble insulin-degrading activity were necessary for this. The mechanism was found to be limited insulin degradation by the soluble enzyme resulting in both trichloroacetic acid-precipitable trichloroacetic acid-soluble fragments followed by further degradtion of the fragments by the glucagon-degrading enzyme resulting in an additional increase in trichloroacetic acid-soluble products.

Animals↗
PubMed1978

Oxidative degradation of pharmaceutically important phenothiazines III: Kinetics and mechanism of promethazine oxidation.

The kinetics of the thermal degradation of promethazine in an acidic medium under various conditions were investigated. The degradation of promethazine and the formation of some degradation products were studied under aerobic and anaerobic conditions. The influence of pH, metal ions such as copper(II) and iron (III), and antioxidants was investigated. In an oxygen-saturated medium, promethazine generally followed first-order kinetics. Increasing the pH increased the degradation rate to a limiting value at pH 5. Addition copper (II) increased the degradation rate over the whole process, while iron (III) caused an increase for only a short time. Ascorbic acid sometimes increased the degradation rate, while higher concentrations of hydroquinone also accelerated the degradation. Pyrosulfite did not have any influence. Under anaerobic conditions, promethazine degraded only in the presence of copper (II) and iorn (III) ions. As a result of the studies on the qualitative and quantitative aspects of the oxidation process, a mechanism for the oxidative degradation of promethazine is suggested. Promethazine 5-oxide and a number of degradation products without intact side chains are formed via a semiquinone free radical. The influence of several factors on the degradation process is discussed.

Antioxidants↗