Studies on the functional significance of a C-terminal S-shaped motif in human arginase type I: essentiality for cooperative effects.

摘要: Abstract The functional significance of a C-terminal S-shaped motif (residues 304–322) in human arginase I was explored by examining the kinetic properties R308A mutant and truncated species terminating either Arg-308 or Ala-308. Replacement with alanine, without truncation, yielded monomeric species. All mutants were kinetically indistinguishable from wild-type enzyme at optimum pH 9.5. At more physiological, 7.5, hyperbolic kinetics observed for all mutants, contrast cooperative behavior exhibited In presence 2 mM guanidinium chloride (Gdn+), single changed to trimeric form, whereas other variants not altered. is suggested as essential response l -arginine 7.5. Gdn+ mimic guanidine group monomer–monomer interface.