PURIFICATION TO HOMOGENEITY AND CHARACTERIZATION OF HOMOSERINE KINASEFROM WHEAT-GERM

Homoserine kinase (EC 2.7.1.39) has been purified from wheat germ to h omogeneity. The native M(r) of the enzyme was estimated by gel filtrat ion to be 75 000. The enzyme seems to be a homodimer with a subunit M( r) of 36 000. No evidence was obtained for the existence of isoforms o f the enzyme. The apparent K(m) values were determined to be 0.24 mM f or homoserine and 0.33 mM for ATP. The enzyme activity was not signifi cantly influenced by any of the aspartate-derived amino acids (threoni ne, methionine, isoleucine, lysine) at least at physiologically releva nt concentrations, nor by L-S-adenosylmethionine which is known to be a regulatory metabolite of the pathway.