Abstract: This chapter describes the assay method, purification procedure, and properties of triokinase. The assay method is based on the measurement of the disappearance of triose substrate in the presence of ATP and magnesium. Triose is estimated by its reducing power after removal of phosphorylated sugars together with proteins by the Ba(OH)2-ZnSO4 reagent. In crude tissue extracts, other reactions than phosphorylation by triokinase may be responsible for triose disappearance, and corrections have to be introduced. Dihydroxyacetone is phosphorylated by the glycerokinase, and so cannot be used as a specific substrate for triokinase. D-Glyceraldehyde is phosphorylated, by triokinase only, to D-glyceraldehyde-3-phosphate which is isomerized to dihydroxyacetone phosphate by triosephosphate isomerase. Under the action of aldolase, the latter compound condenses with a second molecule of D-glyceraldehyde to form fructose-l-phosphate. In the course of purification, it is necessary to measure the amount of fructose-l-phosphate formed in order to be able to calculate the amount of D-glyceraldehyde used by phosphorylation or by condensation. The enzyme is purified from guinea pig liver, and obtained free of glycerokinase. D-Glyceraldehyde and dihydroxyacetone are phosphorylated at approximately the same rate, and these reactions are not inhibited by glycerol even when present in large quantity. L-Glyceraldehyde and D-erythrose are not phosphorylated.
Publication Year: 1962
Publication Date: 1962-01-01
Language: en
Type: book-chapter
Indexed In: ['crossref']
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Cited By Count: 16
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