ISSN 1017-2548(Print)
ISSN 2234-8530(Online)
Volume 23, Number 4
JKCSEZ 23(4)
August 20, 1979 

Glucose 6-phosphate dehydrogenase of Leuconostoc mesenteroides which was purifid by an affinity chromatography was studied on the characterization, kinetics and chemical modification. The apparent molecular weight of the enzyme was 112,000 by the gel filtration method of Sephadex G-200 column. The optimum temperature of NAD+-linked reation was 50℃ and the activation energy and the heat of inactivation were 8.36 kcal/mole and -58.2kcal/mole, respectively. The steady state kinetic study showed KG6P, Kemp, and CX KNADP to be 76.9 PM, 7.46μM and 7.14 μM, respectively, and KGGP, KNAD,and aKNm to be 53.7μM, 115.2μM and 702.2μM for the NAD+-linked reaction at pH 7.8, optimum pH. The pH dependent kinetic constants suggested that the two ionizing groups whose pKa is 7.2 .and pKb is 9.0-9.6 were involved in the enzyme-substrate interaction. Evidence by photooxidation and carboxymethylation of the enzyme suggested that the imidazole group of histidine with pKa group may participate in the catalytic site.