METHANOBACTERIUM-THERMOAUTOTROPHICUM (STRAIN DELTA-H) CONTAINS A MEMBRANE-BOUND CYCLIC 2,3-DIPHOSPHOGLYCERATE HYDROLASE

Cyclic 2,3-diphosphoglycerate (cDPG) hydrolase activity was demonstrat ed in cofactor-free extract of Methanobacterium thermoautotrophicum (s train Delta H), but not in crude extract. Only after ultrafiltration o r dialysis of crude extract cDPG hydrolase activity could be shown. cD PG hydrolysis was optimal at pH 6.0 and 60 degrees C. Hydrolysis of cD PG occurred under nitrogen or hydrogen atmosphere and was completely i nhibited by oxygen. Phosphate and potassium chloride were also strong inhibitors: 50% inhibition occurred at 0.6-0.7 mM phosphate or 0.2 M K CI. The enzyme was localized in the membrane fraction and could be sol ubilized for approximately 60% by treatment with 25 mM of the detergen t CHAPS. The K-m and the V-max for cDPG were determined at 60 degrees C and were 59 mM and 216 mU/mg, respectively. Furthermore, cDPG hydrol ase was dependent on the presence of Co2+. The role of cDPG and cDPG h ydrolase is discussed.