[The nature of phosphate residue binding in the phosphorylated form of succinyl-CoA-synthetase from pigeon breast muscle]. / Izuchenie prirody sviazyvaniia ostatkov fosfata v fosforilirovannoi forme suktsinil-CoA-sintetazy iz grudnoi myshtsy golubia.

The hydrolytic stability of phosphorylated pigeon breast muscle succinyl-CoA synthetase within a wide pH range was studied. It was found that within complex I the phosphate-protein bond is hydrolyzed at alkaline values of pH (11.0 and 13.0); at acidic pH values this bond is hydrolyzed by 50%. Within complex II the phosphate-protein bond is hydrolyzed at acidic pH values and is stable at alkaline pH values. The reaction of the phosphorylated enzyme with hydroxylamine and diisopropylfluorophosphate results in protein dephosphorylation by 50%. Ion-exchange chromatography of the radioactive phosphorylated enzyme II alkaline hydrolyzate (3 n NaOH, 3 hours, 100 degrees C) revealed that the radioactivity was distributed between 1-N-, 3-N-phosphohistidine and 1.3-N-diphosphohistidine fractions. The experimental results suggest that in the phosphorylated enzyme I phosphate is bound to the protein to form an acyl phosphate and phosphoester bonds, while in the phosphorylated enzyme II phosphate binding to the protein occurs with the formation of phosphoamide bonds.