Isolation and characterization of the thermoresistant gluconokinase from Escherichia coli

It is known that two gluconokinases are inducibly expressed during the utilization of gluconate by E. coli . One is thermoresistant (activity stable for 3 h at 30 °C) and the other thermosensitive (losses 75% or more of its activity under the above conditions). The thermoresistant gluconokinase (EC 2.7.1.12) was isolated, purified and characterized for the first time from the E. coli mutant Ca26, a K12 derivative which lacks the thermosensitive activity. The enzyme was purified 43 fold with a recovery of 11%. The M r of the enzyme was 100 kDa with three equal subunits of approximately 29.5 kDa. The enzyme exhibited Michaelis‐Menten kinetics and the K m values for gluconate and ATP were 0.02 mM and 0.045 mM respectively.