THE PURIFICATION AND PROPERTIES OF D-ALLOSEPHOSPHATE ISOMERASE OF AEROBAGTER AEROGENES

Aerobacter aerngenes produces an inducible D-allose 6-phosphate ketol isomerase that nonspecilically isomerizes ribose 5-phosphate. The isomerase was separated from other isomerases present in extracts of cells grown on D-allose by repeated precipitation with protamine. Eighty percent of the activity of the purified preparation was lost on storage at 0 °C for 48 hours. The enzyme was most active and most stable at pH 8.5 and most active at 40 °C. Cobalt, manganese, magnesium, and phosphate ions inhibited at 0.05 M. Mercuric chloride, p-chloromer-curiphenylsulfonate, and iodoacetate also inhibited the isomerase but this was prevented by the addition of cysteine or reduced glutathione. These thiols also reactivated the enzyme when activity was lost during dialysis. 6-Phosphoallonate was a strong inhibitor and to a lesser degree 6-phosphogluconate, 6-phosphoglucosamine, 5-phosphoribonate, and erythrose 4-phosphate. For allose 6-phosphate Ks was 1.2 × 10−3 M and for ribose 5-phosphate, 4.5 × 10−3 M.