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K K Reddi

Publications and source records attributed to K K Reddi.

16 recordsLinked to original sources
PubMed1982

Polycytidylate hydrolysing ribonuclease variants of human pancreas.

Human pancreatic ribonuclease (RNase) comprises three variants with isoelectric points at pH 4.8, pH 9.3 and pH 9.7. These variants are not artifacts of the purification procedure, since they can be demonstrated in crude pancreatic extracts obtained with mild procedures (4). Although these RNase variants differ in their isoelectric points, they are similar in all the other properties so far studied. With polycytidylic acid as a substrate, their activities are optimal in 0.05M sodium phosphate buffer at pH 6.5. Of the several buffers tested, sodium phosphate buffer yielded maximal enzyme activity, but the concentration of phosphate is highly critical. Borate concentrations of 0.05M and 0.1 M respectively brought about 25% and 50% reductions in enzyme activity. Presence of phosphate in the reaction mixture obviates to a great extent the borate inhibition. These RNase variants are highly specific for the secondary phosphate esters of cytidine 3'-phosphate. They have no measurable activity on polyadenylic and polyguanylic acids and their activity on polyuridylic acid is less than 2% of that on polycytidylic acid. These RNase variants could serve as distinctive biochemical markers for the pancreas.

Borates↗
PubMed1980

Serum 5'-nucleotidase of a breast cancer patient.

Serum derived from the breast cancer patient included in this study was found to be a rich source of 5'-nucleotidase. In addition, it also contains nonspecific alkaline phosphatase. The properties of 5'-nucleotidase were studied by eliminating the interference of serum non-specific alkaline phosphatase by the preliminary incubation of serum in glycine-NaOH buffer containing ethylenediamine tetraacetate and magnesium. The enzyme has a pH optimum at 9.5. It is remarkably stable when held at 50 degrees C at pH 7.5, but it readily lost activity in the acid medium at pH 4.2. It hydrolyzes both the ribo- and deoxyribo-nucleoside 5'-phosphates. It has the highest preference for cytidine 5'-phosphate. Adenosine 2'- or 3'- phosphates are refractory to its action.

5'-Nucleotidase↗
PubMed1979

A new phosphatase of human platelets.

Human platelets contain a phosphatase, which has a pH optimum at 7.0. Ethylenediamine tetraacetate and citrate at 0.01 mol/l concentration and Mg2+ at 0.002 mol/l concentration respectively bring about 7.7-, 3.6- and 2.1-fold increase in its activity. It is thermolabile. About 70% of its activity is lost when held at 50 degrees C for 10 min at pH 7.5. On electrophoresis through polyacrylamide gel at pH 8.3, about 87.8% of the total activity remained at the origin and the rest migrated toward the anode. Sodium chloride, potassium chloride, sodium phosphate, ouabain in the absence or presence of K+, potassium tartarte, phenylalanine, sodium fluoride have no effect on its activity. Urea at 1 mol/l and 0.5 mol/l concentrations respectively inhibited about 76% and 28% of its activity. It has the highest preference for p-nitrophenyl phosphate. Its Km and Vmax respectively are 5.7 x 10(-4) mol/l and 2.9 mumol . min-1. Its activity on beta-glycerophosphate is about 0.7% of that on p-nitrophenylphosphate. Its activity on ribo- and deoxyribonucleotides ranges from 0.4% to 3.0% of that on p-nitrophenylphosphate. Its maximum stimulation by EDTA, its non-dependence on K+ and its insensitivity to inorganic phosphate and ouabain, make human platelet neutral phosphatase herein described, distinct from the membrane bound neutral phosphtases so far reported.

Blood Platelets↗
PubMed1978

Serum ribonuclease of normal persons and patients with renal impairment.

Serum ribonuclease of normal persons and of patients with renal impairment was determined with polycytidylic acid as substrate. There was a pronounced rise in the serum ribonuclease of patients with renal impairment. Average serum ribonuclease values of 25 normal persons and 25 patients with renal impairment, respectively were 110 and 2329 units per ml of serum. Serum ribonuclease, because of its unique specificity, stability and abnormal elevation in the sera of patients with renal failure, might serve as an additional indicator in the assessment of renal function.

Creatinine↗
PubMed1977

Purification and properties of a ribonuclease in human urine that hydrolyses polycytidylic acid.

Human urine RNase was purified about 2000-fold. The preparation is free from phosphatase, phosphodiesterase and DNase activities. On electrophoresis through polyacrylamide gel at pH 8.3, it migrates toward the anode and stains with periodic acid-Schiff reagent, suggesting that it is acidic and glycoprotein in nature. Its isoelectric point is at pH 4.1. It has a molecular weight of about 21,500. It is thermostable at pH 4.2 and thermolabile at pH 8.5. It has a pH optimum at 6.5. It exhibits highest preference for cytidine 3'-phosphate linkages. Its activity on poly (C) is endonucleolytic. It cleaves poly (C) via intramolecular transphosphorylation. It has no action on cytidine 2': 3'-cyclic phosphate or uridine 2':3'-cyclic phosphate. Its rate of hydrolysis of poly (U) is less than 2% of that of poly C). Poly (A) and poly (G) are totally inert to its action. Its action on poly (C) is inhibited by poly (G), poly (A) and poly (U). It differs from bovine pancreatic Rnase A in its physical, chemical and catalytic properties. It is, however, similar to human serum and pancreatic RNase in all its properties, suggesting that pancreas is its likely source.

Adult↗
PubMed1976

Elevated serum ribonuclease in patients with pancreatic cancer.

Serum RNase (ribonuclease) of normal persons and of patients with pancreatitis, carcinoma of pancreas, or other neoplasms was determined with poly(C) as substrate. Strikingly abnormal elevations occur in the serum RNase of patients with pancreatic cancer. There is no elevation in the serum RNase level of patients with pancreatitis. Average serum RNase values of 52 normal persons, 10 patients with pancreatitis, 30 patients with pancreatic cancer, 28 patients with breast cancer, 11 patients with lung cancer, 20 patients with colon cancer, six patients with stomach cancer, and four patients with liver cancer, respectively, were 104, 120, 383, 131, 173, 197, 194, and 152 units/ml of serum. Ninety percent of the patients with pancreatic cancer were above the level of 250 units of serum and 90% of all patients with varied cancers were below this level. In the presence of severe renal insufficiency, marked elevation of serum RNase was also observed. Serum RNase, because of its unique specificity, pancreatic origin, and its abnormal elevation in sera of patients with pancreatic cancer, serves as a reliable biochemical marker of carcinoma of the pancreas in the presence of normal renal function.

Carcinoma↗
PubMed1969

Studies on the formation of tobacco mosaic virus ribonucleic acid. 8. Fate of parental viral RNA in the host cell.

Fate of parental viral RNA in the host cell was determined with the use of P(32)-labeled tobacco mosaic virus (TMV)-RNA as inoculum. There was a wide variation in the retention of TMV-RNA that was rubbed on the tobacco leaf surface. On the average, about 0.73 mug of viral RNA was retained by tobacco leaf. About 63 per cent of the retained RNA was degraded in the leaf cells. On the average, about 0.27 mug of TMV-RNA was conserved in a tobacco leaf. The conserved parental TMV-RNA was remarkably stable and was located in the nuclear fraction of leaf homogenate. It could be isolated in an undegraded form and was RNase-sensitive, presumably single-stranded. About 2 per cent of it was associated with progeny TMV.

Cell Nucleus↗