Evidence for the Presence of Two Kinetically Distinct Active Forms of Ribonuclease T2
- 1 February 1981
- journal article
- research article
- Published by Wiley in European Journal of Biochemistry
- Vol. 114 (2) , 229-234
- https://doi.org/10.1111/j.1432-1033.1981.tb05140.x
Abstract
A kinetic study was made of the (Aspergillus oryzae) RNase-T2-catalyzed transphosphorylation of 2 adenine nucleotides, adenylyl(3''-5'')uridine and adenosine 3''-(1-naphthyl)phosphate. Rates were measured at pH values ranging from 2.6-8.2. The observed shape of the plot of log kcat against pH for both the natural and the synthetic substrate suggests that there exist 2 parallel rate-determining pathways. Two pH-independent rate constants and 3 Ki of the enzyme-substrate complexes were obtained by nonlinear iterative least-squares analysis. Detailed interpretation of the pH profiles was carried out and it is proposed that carboxylate anion is likely to deprotonate O-2'' at 4 < pH < 6 but at pH > 6 an alternative general base would play this role more effectively than the carboxylate group. Another base in its protonated cationic form is responsible for the general acid catalysis.This publication has 26 references indexed in Scilit:
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