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Biomedical subjects

A Basu

Publications and source records attributed to A Basu.

At least 253 records · Page 14Linked to original sources
PubMed1984

Characterization of the phospholipid requirement of a rat liver beta-glucosidase.

The lipid requirement of membrane-bound rat liver beta-glucosidase was investigated using 4-methylumbelliferyl-beta-D-glucopyranoside as the substrate. The enzyme was solubilized and delipidated by sequential extraction of a crude lysosomal fraction from rat liver lysosomes with sodium cholate and ice-cold butan-1-ol. Neither saturated nor unsaturated phosphatidylcholine activated this enzyme. In contrast, acidic phospholipids like phosphatidylglycerol (PtdGro) and phosphatidylserine (PtdSer) were effective activators. For the PtdGro series, fatty acid composition was important, with the shorter chain or unsaturated fatty acid-containing PtdGro species being the best activators. Heat-stable factor (HSF) from Gaucher spleen by itself (1-2 micrograms) had no effect on enzyme activity. However, the same amount of HSF when combined with 10 micrograms of PtdSer markedly stimulated beta-glucosidase activity. In the presence of HSF, di-9-cis-octadecenoyl-PtdGro (1 microgram) or -PtdSer (5 micrograms) provided maximum protection of beta-glucosidase against heat (60 degrees C) inactivation. In the absence of phospholipids, HSF had no effect on the rate of inactivation of the enzyme by the suicide inhibitor conduritol B epoxide (t0.5, 12 +/- 0.5 min); the maximum rate of inactivation was achieved in the presence of a mixture of PtdGro (2.5-5 micrograms) and HSF (t0.5, 2.8 min). The combination of PtdSer (10 micrograms) and HSF (1.3 micrograms) lowered the Km for 4-methylumbelliferyl-beta-D-glucopyranoside from 24 to 2.7 mM. Inhibition of the enzyme by the glucocerebrosidase substrate analogues N-hexyl-O-glucosylsphingosine and glucosylsphingosine was influenced by the activator substances. The inclusion of PtdSer and HSF in the beta-glucosidase assay medium lowered the Ki of N-hexyl-O-glucosylsphingosine 20-fold. The same combination of activators decreased the I0.5 of the enzyme for glucosylsphingosine from 89.4 to 7.6 microM. A study of log (Vmax./Km) versus pH indicated that the PtdSer-HSF pair creates the active site of beta-glucosidase, making apparent three ionizable groups on the enzyme with pK values in the range 4.5-5.1.

Animals↗
PubMed1984

Evidence for repetitive structure of the large acyl-carrier protein subunit of Escherichia coli citrate lyase.

The amino acid composition of the unusually large acyl-carrier protein subunit of citrate lyase from Escherichia coli is characteristic of a protein with a highly repetitive structure. Peptide mapping studies provide further evidence of repetitive sequences within the subunit. Only a single Pauly-positive spot is detected in the tryptic peptide map although the subunit contains 8 histidine residues. The 4 prosthetic groups covalently bound to the subunit are recovered in a single tryptic fragment in almost quantitative yield. These structural features of the large acyl-carrier protein subunit probably reflect internal gene duplications.

ATP Citrate (pro-S)-Lyase↗
PubMed1984

Activators of spleen glucocerebrosidase from controls and patients with various forms of Gaucher's disease.

Glucocerebrosidase from normal human spleen, and spleen from cases of neurologic (types 2 and 3) and nonneurologic (type 1) Gaucher's disease, was delipidated and inactivated by extraction from membranes with sodium cholate and ice-cold 1-butanol. Control glucocerebrosidase was stimulated markedly by large quantities (20-30 micrograms/assay) of phosphatidylserine (PS), or by a combination of smaller amounts (1-2 micrograms) of PS and 3 micrograms of a heat-stable factor (HSF) derived from the spleen of a patient with Gaucher's disease. The residual glucocerebrosidase from a nonneurologic case, but not a neurologic case, was also responsive to PS and HSF. The combination of HSF and PS decreased the Km of the normal enzyme for 4-methylumbelliferyl-beta-D-glucopyranoside from 8.0 to 1.6 mM. These effectors also increased the reactivity of glucocerebrosidase to the inhibitor conduritol B epoxide; HSF alone had no effect (t1/2 = 19 +/- 0.5 min) whereas the maximum rate of inactivation (t1/2 = 4.0 min) by conduritol B epoxide was achieved in the presence of a mixture of PS (1 microgram) and HSF (3 micrograms). Phosphatidylglycerol (PG) and phosphatidic acid, also acidic phospholipids, were effective activators of glucocerebrosidase. Varying the fatty acid composition of PG had little effect on its ability to stimulate glucocerebrosidase activity. However, in the case of phosphatidylcholine (PC), a weaker activator than PG or PS, fatty acid composition had a significant impact on the ability of this neutral lipid to activate glucocerebrosidase; dilinoleoyl-PC and dicaproyl-PC were moderately effective activators, but distearoyl-PC and dioleoyl-PC were almost totally inactive. The mono-, and di-, and trisialogangliosides (GM1, GD1, and GT1 were less than half as effective as PS as activators of glucocerebrosidase. These results indicate that acidic phospholipids and the heat-stable factor may both play a role in explaining the genetic heterogeneity of Gaucher's disease.

Enzyme Activation↗
PubMed1984

The effects of lanthanum chloride administration in newborn chicks on glutamate uptake and release by brain synaptosomes.

Acute i.p. administration of lanthanum chloride to newborn chicks at a single dose of 250 mg/kg body weight causes inhibition of the high affinity uptake of [14C]glutamate by isolated brain synaptosomes. There is also a marked decrease in the release of preloaded [14C]glutamate from brain synaptosomes in the presence of externally available Ca2+ (1.2 mM) or a high K+ concentration (71 mM). The inhibition of glutamate release has been discussed in relation to depletion of Ca2+ binding to the synaptosomal membrane under lanthanum intoxication.

Animals↗
PubMed1984

Effects of mercuric chloride on several scavenging enzymes in rat kidney and influence of vitamin E supplementation.

Administration of HgCl2 at a dose of 5 mg/kg body weight/day for 15 days to male albino rats brought about a marked depression of the scavenging enzymes viz. glutathione peroxidase and glutathione S-transferase, in kidney. There was an adaptive rise in the levels of catalase and no increased lipid peroxidation was observed. The levels of both glutathione and glutathione reductase were decreased, whereas total thiol increased. In the intoxicated rats, Vitamin-E was effective in bringing back glutathione levels to normal. The adaptation in this group of animals is reflected by increased superoxide dismutase activities. Feeding of Vitamin-E alone could cause a depression of the scavenging enzymes like glutathione peroxidase and glutathione S-transferase along with a slight lowering of glutathione levels.

Animals↗
PubMed1983

S-acylated residues of the acyl-carrier protein subunit of Klebsiella aerogenes citrate lyase.

Oxidation of the isolated deacetyl acyl-carrier protein subunit of citrate lyase from Klebsiella aerogenes with Cu2+-o-phenanthroline complex leads exclusively to intrapeptide disulfide bridge formation indicating that the cysteamine and the cysteine residues are located in close proximity. The S-acetylation of the cysteine residue in deacetyl acyl-carrier protein subunit is catalysed by a citrate lyase ligase preparation in presence of acetate and ATP. Reaction-inactivation of citrate lyase results in deacetylation of the S-acetyl cysteamine residue of the prosthetic group but not of the S-acylated cysteine residue in the acyl-carrier protein.

Acyl Carrier Protein↗
PubMed1983

The presence of essential arginine residues at the active sites of citrate lyase complex from Klebsiella aerogenes.

The acyl-transferase and acyl-lyase activities of Klebsiella aerogenes citrate lyase complex are inactivated by the arginine specific reagents phenylglyoxal and 2,3-butanedione, the former reagent being the more potent inhibitor. Citrate and (3S)-citryl-CoA protect the transferase activity, while acetyl-CoA markedly enhances the rate of the inactivation. (3S)-Citryl-CoA protects the lyase subunit in the complex from inactivation. The kinetics of inactivation suggest the involvement of a single arginine residue at each of the active sites of the transferase and of the lyase subunits.

Acyl Coenzyme A↗
PubMed1983

Lysis of nitrofurantoin-resistant strain of Vibrio el tor.

Both nitrofurantoin-sensitive and nitrofurantoin-resistant strains of Vibrio el tor were found to lyze in the presence of Tris-EDTA at alkaline pH. The rate of lysis was appreciably enhanced by lysozyme. The amounts of intracellular components, viz. proteins and carbohydrates, released from the nitrofurantoin-sensitive strain by Tris-EDTA treatment, were significantly lower than those from the nitrofurantoin-resistant strain. Differences in periplasmic proteins released from Tris-EDTA treated cells of nitrofurantoin-resistant and -sensitive strains were revealed by gel electrophoresis.

Bacterial Proteins↗
PubMed1982

Photoaffinity labeling of Klebsiella aerogenes citrate lyase by p-azidobenzoyl coenzyme A.

p-Azidobenzoyl coenzyme A functions as a linear competitive inhibitor for (3S)-citryl-CoA in the citryl-CoA oxaloacetate-lyase reaction catalyzed by the Klebsiella aerogenes deacetylcitrate lyase complex (Ki = 80 microM; (3S)-citryl-CoA Km = 67 microM). Inactivation is irreversible on photolysis of p-azidobenzoyl-CoA in the presence of the deacetylcitrate lyase complex. Mg2+ is not required for the inactivation. Inactivation is blocked by (3S)-citryl-CoA in the presence of ethylenediaminetetraacetic acid. p-Azidobenzoyl-CoA has no effect on the acetyl-CoA:citrate CoA transferase activity of both the deacetylcitrate lyase complex and its isolated transferase subunit. The stoichiometry of the CoA ester binding has been investigated by the use of p-azido[14C]benzoyl-CoA as a photoaffinity reagent. The labeling is exclusively on the lyase beta subunit of the citrate lyase complex.

Acyl Coenzyme A↗
PubMed1982

Neurotoxicity of lanthanum chloride in newborn chicks.

Acute intraperitoneal administration of lanthanum chloride to newborn chicks at the single dose of 250 mg/kg body weight inhibits calcium binding to brain synaptosomal membrane. There is also marked depression in the activities of neural Ca2+-ATPase, Mg2+-ATPase, and cholinesterase after acute lanthanum chloride intoxication. The inhibition of these enzymes in relation to depletion of calcium binding to the synaptosomal membrane has been discussed.

Adenosine Triphosphatases↗
PubMed1981

Lysozyme in Schwartz and Moloney virus-induced lymphoblastic leukaemia.

Studies have been made on lysozyme in serum and tissue homogenates in normal and leukaemic mice. An increase in serum lysozyme level occurred in mice bearing both strains of leukaemia as compared to the normal counterparts. Moreover, the elevated enzyme levels seem to be related to the rise in neutrophils in peripheral blood. In the spleen and kidney of leukaemic mice, the lysozyme level was found to be lower than in the normals, while the enzyme level remained more or less unaltered in the liver. The findings are discussed in relation to other reports in the literature.

Animals↗
PubMed1981

Fertility decline and differences in less-developed countries: an anthropological microstudy of some communities of West Bengal, India and Upper Khumbu, Nepal.

The role of socioeconomic and other cultural factors as determinants of fertility change has been widely discussed, with some scholars emphasising an inverse relation between socioeconomic development and fertility, others suggesting that no such relation necessarily exists, and yet others indicating that by using data from various sources it is possible to "prove" that a given country's crude birth rate has declined, remained unchanged or increased. Demographic data are presented on age-sex structure, completed and total fertility rates, and age specific fertility rates by age cohorts of women, from several small, anthropological population units of West Bengal, India and Upper Khumbu, Nepal, exposed to various physical and cultural environmental stresses. The data show that fertility has declined in most of the populations/subpopulations studied and that the decline may, deductively, be attributed to economic development via greater family planning practices.

Adolescent↗