Substrate-induced dissociation of rabbit muscle aldolase into active subunits.

For several years, data have been presented which suggested that the enzyme aldolase, from rabbit muscle, is composed of three subunits of identical, or nearly identical, size and structure (Drechsler et al 1959; Kowalsky -A, and Bayer, 1960; Schachman, 1960; Stellwagen and Schachman, 1962; Deal e al,,19653 Rutter et al 1965; and Winstead and Wold, 1964). More recent 3 data, however, indicate the presence of four subunits of at least two types (Her&wits et al,, 1967; Kawahara and Tanford, 1966; Penhoet et al -A, 1966 and Rajkumar e_t al,> 1966) including the possibility of two identical halfmolecules (Chan and Morse, 1967; Lai et al,,19653 Udenfriend and Velick, 1951). The data to be presented here support this latter model. Materials and Methods Aldolase was prepared from rabbit muscle by the method of Green and Taylor as modified by Drechsler, Boyer and Kowalsky (1959) and recrystallized at least four times to a specific activity of 15-17 units/me protein. Fructose-1,6-diphosphate, sodium salt (FDP) was obtained from Caibfochem; glyceraldehyde-5-phosphate dehydrogenase from Boehringer; and NADH and glycylglycine were obtained from Sigma Chemical Co. Aldolase activity was