The characterization of hexokinase from Trypanosoma rhodesiense and Trypanosoma gambiense.

SYNOPSIS. A hexokinase found in both the soluble and particulate fractions of Trypanosoma gambiense extracts has the following characteristics: A) temperature optimum (50–60°C); B) pH optimum 7.0–9.0; C) required Mg++ and ATP; D) inhibited by ADP, p-hydroxymercuribenzoate and also competitively inhibited by mannose, glucosamine and N-acetyl-D-glucosamine; E) phosphorylated glucose (km 2.8 × 10-4 M), fructose (km 1.4 × 10-3 M), mannose (km 2.6 × 10-4 M), 2-deoxy-D-glucose, and glucosamine. This enzyme was clearly distinguished from yeast hexokinase on the basis of its temperature optimum, inhibition by sulfhydryl inhibitors, and immunological specificity. The inhibition by p-hydroxymercuribenzoate would suggest a similarity to the animal hexokinases. It has also been found that this enzyme is not the rate limiting step in carbohydrate metabolism. Therefore, differences in the rate of hexose utilization by T. gambiense cannot be accounted for by differences in the rate of phosphorylation of various hexoses. The enzyme from T. rhodesiense has not been as completely characterized as the enzyme from T. gambiense; however, the preliminary results would suggest a close similarity in their properties.