Two isozymes of chicken muscle acylphosphatase: purification and properties

Two acylphosphatases, named Ch1 and Ch2, have been purified from chicken skeletal muscle. The molecular weights were determined to be 11,900 and 12,000 for Ch1 and Ch2, respectively, by sedimentation equilibrium. In the amino acid compositions of Ch1 and Ch2, two residues of histidine were contained in Ch2, but none in Ch1, and one residue of cysteine was contained in Ch1, but none in Ch2. There were 11 lysines and 6 arginines in Ch1, whereas there were 6 lysines and 11 arginines in Ch2. In addition, the contents of methionine, serine, glutamic acid and glutamine, and alanine were considerably different between Ch1 and Ch2. There were also differences in the peptide maps and carboxyl-terminal amino acid sequences (-Ser-Thr-Arg-Tyr-COOH for Ch1, and -Phe-Thr-Ile-Arg-Lys-COOH for Ch2). In the double immunodiffusion, Ch2 did not form a precipitin line with the rabbit anti-Ch1 antiserum. These results indicate that Ch1 and Ch2 are different, genetically specified isozymes of acylphosphatase of chicken skeletal muscle. Ch2 is considered to be a new type of acylphosphatase from skeletal muscle.