Stability properties of human brain apo-transketolase

Stability properties of human brain apo-transketolase were investigated by studying the effect of a range of pH (6.25 to 8.20) at 37 degrees C on it as well as the effect of storage for different time intervals ranging from 10 to 210 min. The results show that initial rate of loss of enzyme activity is pH dependent, being minimal at a pH value of 7.6 at 37 degrees C (which is equivalent to pH 8.0 at room temperature of 20 degrees C). This optimum pH for human brain apo-transketolase in vitro is close to that likely to exist in vivo as well as that for rat brain enzyme reported previously. The findings on the stability of the brain enzyme during storage suggest that the human apo-transketolase is more stable than the rat apo-transketolase since 20% of enzyme activity is lost in approximately 180 min of incubation compared to 50% loss reported in the rat brain. Hence, it can be concluded that although the human brain apo-transketolase is identical to the rat enzyme in that they both an optimum pH of 7.6 at 37 degrees C, the human brain enzyme appears to be more stable than the rat enzyme. The instability of the human brain apo-transketolase, together with the variant forms of the human erythrocyte transketolase, provides further support for the role of transketolase in the genesis of alcoholic brain damage.