Browsing by Author "Dua, R D"
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Item Carboxypeptidases from buffalo pancreas: purification and characterisation of two forms of carboxypeptidase A.(1984-04-01) Sud, M; Dua, R DItem Carboxypeptidases from goat pancreas.(1973-09-01) Dua, R D; Dixit, AItem Characterization of prosthetic groups of naphthalene oxygenase from Corynebacterium renale.(1985-02-01) Srivastava, M; Dua, R DItem Effect of biologically occurring (poly) cationic compounds on some of the pancreatic activities.(1980-08-01) Singh, C; Anjaneyulu, K; Dua, R DItem Endogenous inhibitor of carboxypeptidase A from goat pancreas.(1975-06-01) Dua, R D; Bedi, G S; Dixit, AItem Evidence for suggested mechanism of goat carboxypeptidase A catalyzed hydrolysis of acylpeptides.(1987-04-01) Dua, R D; Gupta, KItem Mechanism of action of goat pancreatic carboxypeptidase B: part I--role of arginine residue at the active centre.(1980-04-01) Srivastava, S K; Dua, R DItem Mechanism of action of goat pancreatic carboxypeptidase B: Part II--role of tyrosine & glutamate/aspartate residues at the active centre.(1980-06-01) Srivastava, S K; Dua, R DItem Mechanistic studies on carboxypeptidase A from goat pancreas Part I: Role of tyrosine residue at the active site.(1984-12) Dua, R D; Gupta, KamleshChemical modification of carboxypeptidase Ag1 from goat pancreas with Nacetylimidazole or iodine led to loss of enzymic activity. This loss in activity could be prevented when chemical modification was carried out in the presence of β-phenylpropionic acid or substrate NCbz-glycyl-L-phenylalanine, thus suggesting a tyrosine residue at the active site. Chemical modification of tyrosine was confirmed by spectral and kinetic studies. While tyrosine modification destroyed peptidase activity, esterase activity of the enzyme remained unchanged thus indicating non-involvement of tyrosine residue in ester hydrolysis.Item Mechanistic studies on carboxypeptidase A from goat pancreas Part II: Evidence for carboxyl group.(1985-09) Dua, R D; Gupta, KamleshStudies with substrate analogues and the pH optimum indicated the involvement of carboxyl group in the active site of goat carboxypeptidase A. Chemical modification of the enzyme with 1-cyclohexyl-3-(2-morpholinoethyl) carbodiimide methoI -p-toluene sulphonate, a carboxyl specific reagent, led to loss of both esterase and peptidase activities. Protection studies showed that this carboxyl group was in the active site and was protected by ßphenylpropionic acid and glycyl-L-tyrosine. Kinetic studies also confirmed the involvement of carboxylic group because the enzyme modification with water soluble carbodiimide was a two step reaction which excluded the possibility of tyrosine or lysine which are known to give a one step reaction with this reagent.Item Metal ion requirement of goat carboxypeptidase B.(1976-12-01) Rao, M P; Dua, R DItem Modification of carboxyl group at the active site of liquefying alpha-amylase.(1985-10-01) Dua, R D; Kochhar, SItem Partial purification and characterisation of carboxypeptidase B from goat pancreas.(1975-03-01) Rao, M P; Dua, R DItem Persistence of typable activity of pseudocholinesterase (E2 locus) -C5 component polymorphism in human bloodstains under Indian climatic conditions.(1979-03-01) Joshi, H; Sivaram, S; Dua, R DItem Photo-oxidation of goat pancreatic carboxypeptidase B & role of histidine residues at its active site.(1980-06-01) Srivastava, S K; Dua, R DItem Product stabilization of the two forms of carboxypeptidase A from buffalo pancreas.(1985-09) Sud, Mir; Dua, R DThe two forms of buffalo carboxypeptidase A lose a part of their activity when incubated at their optimal temperature. Both the forms are protected from heat denaturation by L-phenylalanine, one of the reaction products while the other reaction product hippuric acid provides only limited protection. It has also been shown that L-phenylalanine and hippuric acid bind at the same site of the enzyme and that the release of L-phenylalanine follows that of hippuric acid. On this basis, a new mechanism for the hydrolysis of acyldipeptides by carboxypeptidase A has been proposed.Item Purification & substrate specificity of carboxypeptidase B from goat pancreas.(1976-06-01) Dua, R D; Anand, R C; Hussain, A; Rao, M PItem Purification and characterization of carboxypeptidase A from goat pancreas.(1973-09-01) Dixit, A; Dua, R DItem Purification and preliminary characterization of L-asparaginase from Erwinia aroideae NRRL B-138.(1996-10-01) Tiwari, N; Dua, R DL-Asparaginase (L-asparagine amidohydrolase EC 3.5.1.1) from Erwinia aroideae NRRL B-138 has been purified to apparent homogeneity by ammonium sulphate precipitation, chromatography on sulfopropyl-sephadex C-50 and sephadex G-200 with 22% recovery and 567-fold purification. The enzyme obtained from sulfopropyl-sephadex C-50 was unstable and lost activity within a few hours. Addition of glycerol helped in restoring the activity of the enzyme. The enzyme has an apparent molecular mass of approximately 155 kDa and has four subunits of identical molecular mass of approximately 38 kDa. The K(m) for L-asparagine is 2.8 x 10(-3) M. Enzyme shows optimal activity at 45 degrees C and pH 8.2. Energy of activation as determined from Arrhenius plot was 9.1 kcal/mol. Substrate L-asparagine and analogue L-glutamine, D-asparagine and 6 diazo-5-oxo-L-norleucine provide full protection to the enzyme against thermal denaturation.