Inactivation of ribulosebisphosphate carboxylase by modification of arginyl residues with phenylglyoxal. [Spinach, Rhodospirillum rubrum]
Phenylglyoxal rapidly and completely inactivates spinach and Rhodospirillum rubrum ribulosebiphosphate carboxylases. Inactivation exhibits pseudo-first-order kinetics and a reaction order of approximately one for both enzymes, suggesting that modification of a single residue per protomeric unit suffices for inactivation. Loss of enzymic activity is directly proportional to incorporation of (/sup 14/C)phenylglyoxal until only 30% of the initial activity remains. For both enzymes, extrapolation of incorporation to 100% inactivation yields 4 to 5 mol of (/sup 14/C)phenylglyoxal per mol protomer. Amino acid analyses confirm the expected 2:1 stoichiometry between phenylglyoxal incorporation and arginyl modification and suggest that other kinds of amino acid residues are not modified. (Thus, inactivation correlates with modification of 2 to 3 arginyl residues per protomer.) The substrate ribulose bisphosphate and some competitive inhibitors reduce the rates of inactivation of the carboxylases and prevent modification of about 0.5 to 1.0 arginyl residue per protomer. Inactivation is therefore a consequence of modification of a small number of residues out of the 35 and 29 total arginyl residues per protomer in spinach and R. rubrum carboxylases, respectively.
- Research Organization:
- Oak Ridge National Lab., TN
- OSTI ID:
- 6531963
- Journal Information:
- Biochemistry; (United States), Vol. 17:26
- Country of Publication:
- United States
- Language:
- English
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