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At least 19 recordsLinked to original sources
PubMed1978

Nonenzymatic hydrolysis reactions of adenosine 5'-triphosphate and its related compounds. III: Catalytic aspects of some cobalt(III) complexes in ATP-hydrolysis.

Trichlorodiethylenetriaminecobalt (III), [CoCl3dien], which is provided with three good leaving ligands and, hence, capable of binding ATP in a characteristic mode, accelerated effectively and specifically hydrolysis of ATP to ADP and Pi. A kinetic study of the reaction indicated that the rate of hydrolysis was first order with respect to the concentration of ATP in the presence of an excess of [CoCl3dien]. The rate constant was calculated to be 1.05 X 10(-2) min-1 at pH 4.0 (50 degrees C), corresponding to a catalysis of the hydrolysis of ATP by a factor of 150. The complex possessing one good leaving ligand, chlorotetraethylenepentaminecobalt(III), and that having two of them in trans-position, dichlorobis(dimethylglyoximato)cobalt(III) only slightly enhanced the hydrolysis of ATP. Dichloro-cis-alpha- and dichloro-cis-beta-triethylenetetraminecobalt(III) complexes, which have two good leaving ligands and allow chelation of ATP in their coordination sphere, exhibited fairly good activities, although the hydrolysis reactions of ATP occurred in two modes as ATP leads to ADP + Pi and ATP leads to AMP + PPi. The mechanism of ATP-hydrolysis reaction with [CoCl3dien] was also discussed on the basis of the kinetic data.

Adenosine Diphosphate↗
PubMedDate not supplied

[Asparagine metabolism in mycobacteria. II. -- Asparagine hydrolysis and aspartohydroxamic acid formation and hydrolysis catalysed by M. fortuitum, M. phlei and BCG asparaginases (author's transl)].

Crude extracts of BCG, M. fortuitum and M. phlei, hydrolyse asparagine (I) and L-beta-asparthohydroxamic acid (III), and catalyse the synthesis of aspartohydroxamic acid from asparagine and hydroxylamine (II). The ratio between these enzymatic activities (I:II and I:III) presents a certain stability during the different steps of purification of these mycobacteria asparaginases. In particular, M. fortuitum asparaginase has been purified 90 to 130-fold, with recovery of approximately 10%. Only the fractions of supernatants which have an asparaginase activity catalyse the formation of aspartohydroxamate from asparagine and hydroxylamine. Some differences between the asparaginases of these strains are described. Particularaly, in comparison to reaction I, their abilities to catalyse reactions II and III vary noticeably from one asparaginase to an other. The asparaginase of BCG catalyses very slightly in the reactions II and III and is more specific of L-asparagine hydrolysis than are the asparaginases of M. fortuitum and of M. phlei. Furthermore, in the case of M. phlei, p-chloromercuribenzoate (pCMB) inhibits very stronly the reactions I and III and slightly reaction II, whereas conversely, for M. fortuitum, pCMB does not inhibit reactions I and III but strongly inhibits reaction II. In the case of BCG, these three reactions are not inhibited by pCMB. Moreover, the asparaginases from these strains are more or less sensitive to the ionic strength of the buffer used.

Asparaginase↗
PubMed1975

Hydrolysis of nucleoside phosphates: IV. The metal ion-nucleic base interaction in the Cu2+-promoted dephosphorylation of the 5'-di- and 5'-triphosphates of cytidine, inosine and guanosine, and their protection toward hydrolysis by coordination to Cu(2,2'-bipyridyl)2+.

The dephosphorylation of CTP, GTP, ITP, ATP, CDP, GDP, IDP and ADP was characterized by measuring the first-order rate constant (50 degrees; I = 0.1, NaClO4) in dependence on pH (2 to 10). Except with CTP and CDP, the reactions are significantly accelerated by Cu2+ and pass through pH optima. By computing the pH dependence of the distribution of the several species present in the nucleotide (NP) systems, it is shown that the most reactive species is Cu(NP). Cu(NP-H), where N(1) is deprotonated, is somewhat less reactive. In both types of complexes, a metal ion-nucleic base interaction, which is responsible for the increased reactivity, occurs, i.e., macrochelates involving the phosphate chains and the base moieties are formed. In accord herewith, CTP and CDP are rather stable as the coordination tendency of the cytosine moiety is small. Furthermore, in the ternary complexes Cu(2,2'-bipyridyl)(NP) and Cu-(2,2'-bipyridyl)(NP-H), where the formation of a macrochelate is inhibited, the nucleotides are protected. The structure-reactivity relationship is also evident with Cu(ITP)2- and Cu(IDP)- which exist only in part as macrochelates; hence, they are less reactive than for example Cu(ATP)2- or Cu(ADP)-. With the aid of the initial rate, vo = d[PO4(3-)]/dt, the rate laws of the ascending side of the pH optima were determined: vo = k[Cu(NP)]/[H+]. A reaction mechanism that includes an intermolecular attack of OH- at the terminal phosphate group is proposed. The descending side of the pH optimum is attributed to the formation of CU(NP)(OH) or Cu(NP-H)(OH), where the Cu2+-base interaction is insignificant. However, these hydroxy complexes are still somewhat faster dephosphorylated than the free nucleotides. This is attributed to an intramolecular attack of the bound OH- at the terminal phosphate group.

2,2'-Dipyridyl↗
PubMed1978

Enzymatic hydrolysis of soy protein for nutritional fortification of low pH food.

Enzymatic hydrolysis of proteins is an attractive means of obtaining the changes in the functional properties often necessary for incorporating the protein in low pH food, e.g. soft drinks. The main problem associated with protein hydrolysis is the welldel-known formation of bitter-tasting peptides. The bitterness seems to be related to a too high degree of hydrolysis (DH). DH is defined as the percentage of cleaved peptide bonds and serves as the controlling parameter for the hydrolysis process. The choice of hydrolysis parameters is briefly discussed in relation to studies on the hydrolysis kinetics which in many respects can be described by classical enzyme kinetics. Several pilot plant productions of isoelectric soluble soy protein hydrolyzates have been carried out using soy isolate or soy concentrate as the raw material. The preferred enzyme for this type of hydrolysis is Alcalase 0.6 L, a food-grade liquid preparation of subtilism Carlsberg. The chosen hydrolysis parameters are : Substrate conc. : 8 per cent protein (N x 6.25). Enzyme-substrate ratio : 2 per cent. pH : 8.0. Temperature : 50 degrees C. The optimal DH value with regard to taste seems to be 10 per cent, corresponding to about 2 hours' hydrolysis time. The hydrolysis is terminated by the addition of citric or malic acids until pH reaches a value of 4.2. Separation of the supernatant from the unconverted protein is carried out in a continuous, solids-ejecting centrifuge. Preliminary rat trials show a satisfactory nutritional quality of the hydrolyzates. Possible end-uses for soy protein hydrolyzates are briefly discussed.

Food, Fortified↗
PubMed1978

The hydrolysis of bile acid conjugates.

Studies were made of a) the relationship of bile acid structure and analytical recoveries (measured by 3-hydroxysteroid oxidoreductase) following vigorous alkaline hydrolysis of bile acid conjugates and b) the relationship of structure and hydrolysis time of taurine- and glycine bile acid conjugates in a reaction catalyzed by glycocholic acid hydrolase. Alkaline hydrolysis resulted in good recoveries of hydroxy and 7 and 12- oxo-bile acids but poor recoveries of 3-oxo-bile acids. Borohydride reduction of the 3-oxo-acids prevented these losses. Complete enzymatic hydrolysis of glycine conjugated bile acids was about five times more rapid than that of taurine conjugates. Hydrolysis of conjugates containing oxo groups was slow. Borohydride reduction of oxo-acids corrected this and did not inhibit enzymatic hydrolysis. It was concluded that both vigorous alkaline and enzymatic hydrolysis are satisfactory in bile acid assays if borohydride reduction is instituted before the hydrolytic step. However, due to the presence of possible enzyme inhibitors and solubility difficulties, strong alkaline hydrolysis is preferable to enzymatic hydrolysis in fecal bile acid determinations at this time.

Amidohydrolases↗
PubMed1979

Hydrolysis of membrane phospholipids by phospholipases of rat liver lysosomes.

(1) The hydrolysis of (32)P- or myo-[2-(3)H]inositol-labelled rat liver microsomal phospholipids by rat liver lysosomal enzymes has been studied. (2) The relative rates of hydrolysis of phospholipids at pH4.5 are: sphingomyelin>phosphatidylethanolamine>phosphatidylcholine> phosphatidylinositol. (3) The predominant products of phosphatidylcholine and phosphatidylethanolamine hydrolysis are their corresponding lyso-compounds, indicating a slow rate of total deacylation. (4) Ca(2+) inhibits the hydrolysis of all phospholipids, though only appreciably at high (>5mm) concentration. The hydrolysis of sphingomyelin is considerably less sensitive to Ca(2+) than that of glycerophospholipids. (5) Analysis of the water-soluble products of phosphatidylinositol hydrolysis (by using myo-[(3)H]inositol-labelled microsomal fraction as a substrate) produced evidence that more than 95% of the product is phosphoinositol, which was derived by direct cleavage from phosphatidylinositol, rather than by hydrolysis of glycerophosphoinositol. (6) This production of phosphoinositol, allied with negligible lysophosphatidylinositol formation and a detectable accumulation of diacylglycerol, indicates that lysosomes hydrolyse membrane phosphatidylinositol almost exclusively in a phospholipase C-like manner. (7) Comparisons are drawn between the hydrolysis by lysosomal enzymes of membrane substrates and that of pure phospholipid substrates, and also the possible role of phosphatidylinositol-specific lysosomal phospholipase C in cellular phosphatidylinositol catabolism is discussed.

Animals↗
PubMed1979

Evidence for the presence of two separate protein activators for the enzymic hydrolysis of GM1 and GM2 gangliosides.

Two different protein activators were isolated simultaneously from human liver for the enzymic hydrolysis of GM1 (Gal beta 1 leads to 3GalNAc beta 1 leads to 4Gal(3 comes from 2 alpha NeuAc)beta 1 leads to 4Glc-Cer) by beta-galactosidase and GM2 (GalNAc beta 1 leads to 4Gal(3 comes from 2 alpha NeuAc)beta 1 leads to 4Glc-Cer) by beta-hexosaminidase A. The hydrolysis of GM1 is stimulated only by the GM1-specific activator which has very little effect on the hydrolysis of GM2. The same is also true for the hydrolysis of GM2. The antiserum raised against GM1 activator did not cross-react with GM2 activator and vice versa. These results suggest the presence of two different activators for the separate hydrolysis of GM1 and GM2. In connection with the enzymic hydrolysis of GM1 and GM2, we found that the hydrolysis of GM2 by human hepatic beta-N-acetylhexosaminidase A was severely inhibited by a buffer of high ionic strength, whereas no such inhibition was observed in the hydrolysis of GM1 by beta-galactosidase.

Enzyme Activation↗
PubMedDate not supplied

[Hydrolysis of insoluble collagen of bull bones by Streptomyces griseus crystalline protease].

Hydrolysis of collagen was studied in the bull bone tissues by the Str. griseus crystalline protease. The amount of collagen hydrolyzed by it composed 6.6% and 16% after 4-hour and 6-hour hydrolysis, respectively. When the enzyme:substrate ratio is 1:50 hydrolysis proceeds most intensively; with a decrease in the ratio up to 1:1000 the average amount of peptides increase from 2.6 up to 4 amino acidic residua, respectively. Under conditions of denaturated collagen hydrolysis the content of hydroxyproline in solution as compared with the native one increases; in this case the links with the presence of imino-acids are easier to split, the more resistant being those formed by hydroxyproline. Within the limit of 20-45 degrees C hydrolysis of protein intensifies with a temperature rise. Within the pH range of 5.0-11.0 the maximal amount of alpha- NH2-groups and hydroxyproline is observed at pH 8.5, the minimal--at PH 5.0. Hydroxyproline in the composition of peptides appears at the beginning of hydrolysis whereas the free one of enzymes of the longer effect 24 h after the beginning of the experiment composes 12.2% of its total content in the solved products. In the insoluble part of the substrate after 3-hour hydrolysis tyrosine composes less than 25% of its initial amount in protein whereas phenyl alanine--over 70%. After 6-hour hydrolysis the solved part of the system contains about 30% of alanine and 8.9 and 6% of glycine, proline and hydroxyproline, respectively.

Amino Acids↗
PubMed1976

Adenosine triphosphate hydrolysis in rat dental tissues. A histochemical study of ion dependencies.

The effect of EDTA-decalcification, reactivating and activating procedures on the hydrolysis of ATP was studied histochemically in developing dental tissues in the rat. The incubation media contained lead citrate at alkaline pH and lead nitrate at neutral pH, and the results with ATP as substrate were compared with those obtained with beta-glycerophosphate. The ion dependency of ATP hydrolysis could only be ascertained in decalcified sections. As in earlier studies on the hydrolysis of beta-glycerophosphate in dental tissues, this hydrolysis could readily be reactivated through preincubation of the sections in a series of 0.1 M solutions of divalent cations; Zn2+ being the most efficient. This treatment was now found also to give rise to an ATP hydrolysis, which occurred without the need for activating ions in the incubation medium. This ATP hydrolysis should thus be described as nonspecific and, in terms of ion dependency, as due to a metalloenzyme, i.e. alkaline phosphatase. Activating ion dependent ATP hydrolysis in the dental tissues was found in the blood vessels and in the apical part of the secretory ameloblasts. The former was activated by Mg2+, Ca2+ and Mn2+, and the latter by Ca2+ and--almost specifically--by Sr2+. Preincubation with Zn2+ always inhibited the ion dependant ATP hydrolysis in the dental tissues.

Adenosine Triphosphatases↗
PubMed1979

Factors affecting the hydrolysis of ceramide-3 by alpha-galactosidase A from human liver.

1. The effect of detergents on the catalytic properties of alpha-galactosidase from human liver was studied using p-nitrophenyl-alpha-galactoside and galactosyl-alpha(1 leads to 4)-galactosyl-beta(1 leads to 4)-glucosylceramide (ceramide-3) as substrates. 2. The hydrolysis of p-nitrophenyl-alpha-galactoside by alpha-galactosidase was inhibited by commercial preparations of sodium taurocholate and by taurocholate purified from these preparations by thin-layer chromatography. The extent of inhibition was dependent on the concentration of the detergent and on the amount of protein present. The impurities present in the preparation also inhibited the hydrolysis. 3. The inhibition of taurocholate preparations of p-nitrophenyl-alpha-galactoside hydrolysis was pH-dependent. 4. The inhibition by taurocholate of p-nitrophenyl-alpha-galactoside hydrolysis can be partly overcome by adding glycosphingolipids. 5. No significant hydrolysis of ceramide-3 occurs in the absence of detergent. Upon adding increasing concentrations of taurocholate, the rate of hydrolysis increases to a maximum value. At still higher taurocholate concentrations the activity decreases. 6. The concentrations of taurocholate giving a maximal rate of hydrolysis of ceramide-3 is dependent on the amount of protein present and independent of the ceramide-3 concentration. 7. When the pH dependence of the rate of hydrolysis of ceramide-3 was measured in the presence of a commercially available preparation of pure taurocholate or of crude taurocholate, curves with different shapes were obtained.

Ceramides↗
PubMed1975

Hot hydrochloric acid hydrolysis and UV Feulgen staining of rat liver sections fixed in CRAF and CRAF-like fixative.

Sections of rat liver fixed in CRAF III and Nawaschin's fixative in Dutt's modification were subjected to hydrolysis in 1N HCl at 60 degrees C for different periods of time and to Schiff's staining according to the UV Feulgen technique. The study showed that Feulgen reaction intensity depends upon time of hydrolysis, optimum coloration being possible only after 10-15 min of hydrolysis. Prolongation of hydrolysis beyond this time produced decreased staining intensity which is retained for further 35 min of hydrolysis thus forming a plateau. Further prolongation of hydrolysis results in gradual deterioration of the staining intensity which culminates in utterly pale coloration of the nuclei after one hour's hydrolysis. A possible explanation for this phenomena is suggested.

Animals↗
PubMed1977

The effect of sodium chloride on the extraction of DNA fragments during Feulgen acid hydrolysis.

Feulgen acid hydrolysis was performed on ascites tumour cells labelled with radioactive DNA-precursors. The development of fragments of apurinic acid and the extraction of purines were studied by monitoring the variations in the extraction rate during the hydrolysis when sodium chloride was either present or absent from the hydrolysis solution. The changes in the rate of extraction of purines and the alterations in the initial retardation of the apurinic acid extracting process followed approximately the same pattern. The extractability of apurinic acid fragments during hydrolysis in 0.3 M HCl was found to be a maximum when the sodium chloride concentration was about 1 M. Sudden exchange experiments, in which acid was substituted for sodium chloride after various times of hydrolysis, revealed a successive shortening of the extractable fragments during the low acid concentration hydrolysis. The results strengthen the view that, during hydrolysis, apurinic acid is lost from the cells through a reaction whose form is determined, first, by an initial retardation of the depolymerization, second, by the maximum length at which fragments developed through the depolymerization become soluble and are lost by diffusion, and last, at low acid concentrations, by a mechanism whose influence is equivalent to the presence of bonds between the fragments and an unextractable stable structure.

Animals↗
PubMed1979

Studies on the mechanism of enzymatic hydrolysis of cellulosic substances.

Most cellulosic substances contain appreciable amounts of cellulose and hemicellulose, which on enzymatic hydrolysis mainly yield a mixture of glucose, cellobiose, and xylose. In this paper, studies on the mechanisms of hydrolysis of bagasse (a complex native cellulosic waste left after extraction of juice from cane sugar) by the cellulase enzyme components are described in light of their adsorption characteristics. Simultaneous adsorption of exo- and endoglucanases on hydrolyzable cellulosics is the causative factor of the hydrolysis that follows immediately after. It supports the postulate of synergistic enzyme action proposed by Eriksson. Xylanase pretreatment enhanced the hydrolysis of bagasse owing to the creation of more accessible cellulosic regions that are readily acted upon by exo- and endoglucanases. The synergistic action of the purified exoglucanase, endoglucanase, and xylanse has been found to be most effective for hydrolysis of bagasse but not for pure cellulose. Significant quantities of glucose are produced in beta-glucosidase-free cellulase action on bagasse. Individual and combined action of the purified cellulase components on hydrolysis of native and delignified bagasse are discussed in respect to the release of sugars in the hydrolysate.

Adsorption↗