Comparative enzymology of 5′-AMP aminohydrolase from normal and genetically dystrophic chicken muscle

Abstract

A comparative study of the functional and structural properties of homogeneous 5′-adenylic acid aminohydrolase (EC 3.5.4.6) from normal and dystrophic chicken muscle is presented. Dystrophic chickens (New Hampshire Reds) were obtained from the University of California Experiment Station at Davis. Breast muscle from adult (1-year-old) lines 200 (normal), 304, and 307, from 12-week-old line 307, and commercially available chickens, and mixed leg and thigh muscle from 12-week-old line 307 and commercially available chickens were used as the source of the enzyme. The enzyme from each source had the same kinetic properties, subunit, native molecular weight, and rate of inactivation by heat, papain, and chymotrypsin. The enzyme from lines 200 and 307 1-year-old chicken breast muscle had the same amino acid composition within the error of the analysis. Neither enzyme had a reactive N-terminal amino acid as determined by the dimethylaminonapthalene sulfonyl chloride reaction. The enzyme from lines 304 and 307 and normal chicken breast muscle also had the same immunochemical properties. On the other hand, the enzyme from dystrophic muscle from normal dark mixed leg and thigh muscle and from normal breast muscle have differing isoelectric points. Normal breast muscle enzyme has a pI = 5.6–5.7, normal dark mixed leg and thigh muscle enzyme, pI = 6.2, and dystrophic breast and mixed leg and thigh muscle pI = 6.1. Recent evidence (32) shows that the enzyme is a glycoprotein and that the enzyme from dystrophic muscle has an altered carbohydrate composition.