Modification of arginyl and lysyl residues of flavokinase from rat small intestine.
The amino acid composition of flavokinase has been determined to contain five arginyl and four lysyl residues per mole. Flavokinase is inactivated by arginine-specific reagents. The substrates riboflavin and especially ATP impede inactivation, whereas neither of the products, ADP or FMN, protect. Among lysine-modifying reagents, only 2,4,6-trinitrobenzene sulfonic acid caused inactivation of the enzyme, especially under conditions for denaturation. In this case it was noted that the activity was enhanced at the early stage of the reaction but this enhancement was repressed in the presence of ATP along with the significant protection of activity. Results with modification of arginyl residues and incorporation of 14C-phenylglyoxal suggest that one such residue is involved in the substrate-binding site. The involvement of lysyl residues in catalytic function remains unclear, but seems less critical.
Nakano
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Department of Biochemistry, Rollins Research Center, School of Medicine, Emory University, Atlanta, GA 30322.
McCormick
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DB
D000244:Adenosine Diphosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000596:Amino Acids / Q000032:analysis; D000818:Animals; D001120:Arginine / Q000378:metabolism*; D007421:Intestine, Small / Q000201:enzymology*; D008239:Lysine / Q000378:metabolism*; D010422:Pentanones / Q000737:chemistry; D010658:Phenylglyoxal / Q000737:chemistry; D010770:Phosphotransferases / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism*; D017853:Phosphotransferases (Alcohol Group Acceptor); D051381:Rats
D000596:Amino Acids; D010422:Pentanones; C008790:acetylacetone; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D001120:Arginine; D010770:Phosphotransferases; D017853:Phosphotransferases (Alcohol Group Acceptor); C022532:riboflavin kinase; D008239:Lysine; D010658:Phenylglyoxal