Thiamin-triphosphate-synthesizing activity of mutant cytosolic adenylate kinases: significance of Arg-128 for substrate specificity.
The thiamin triphosphate (TTP)-synthesizing activity and the ATP-synthesizing activity of two mutant enzymes of chicken cytosolic adenylate kinase whose Arg-128 was substituted by Trp (cAK1(Trp)) or Ala (cAK1(Ala)) were compared to those of the wild-type enzyme. The TTP-synthesizing activity of both the mutant enzymes was higher due to higher affinity to thiamin diphosphate (cAK1(Trp)) or a larger Vmax (cAK1(Ala)). The optimal pH shifted to pH 9.0 from pH 10.5. The ATP-synthesizing activity of both the mutant enzymes was, on the other hand, markedly decreased with lower affinity for ADP and lower Vmax. These results suggest that Arg-128 plays an important role in the substrate specificity of the cytosolic adenylate kinase.
Shioda
T
T
Department of Biochemistry, Hiroshima University School of Medicine, Japan.
Yasuda
S
S
Yamada
K
K
Yamada
M
M
Nakazawa
A
A
Kawasaki
T
T
D000263:Adenylate Kinase / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D000818:Animals; D001120:Arginine / Q000378:metabolism*; D002645:Chickens; D003600:Cytosol / Q000201:enzymology; D004591:Electrophoresis, Polyacrylamide Gel; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D009154:Mutation; D013379:Substrate Specificity; D013696:Temperature; D013838:Thiamine Triphosphate / Q000378:metabolism*
D013838:Thiamine Triphosphate; D001120:Arginine; D000263:Adenylate Kinase