Glyceric Acid Kinase Isolated From a Polish Variety of Rapeseed (Brassica Campestris L.)

Glyceric acid kinase from Polish variety rapeseed (Brassica campestris L.) was purified approximately 30-fold by ammonium sulphate fractionation and adsorption on alumina Cγ gel. The enzyme has a pH optimum at 7.9 and a pH stability range extending from 6.5 to 7.5. The maximum temperature for the reaction was 45 °C. The phosphorylation required ATP and a metal ion; Mg++was slightly more effective than Mn++and Co++, while Ni++and Zn++were ineffective. The Michaelis constants for the Mg–ATP complex and the substrate were 7.3 × 10−4 M and 1.6 × 10−3 M respectively. The reaction products, ADP and 3-phosphoglyceric acid, inhibited the phosphorylation. Sulphydryl reagents such as p-chloromercuribenzoate, o-iodosobenzoate, N-ethylmaleimide, and iodo-acetate completely inhibited the enzyme at low concentrations. 3-Phosphoglyceric acid was isolated and characterized from the enzyme reaction mixture.