Hexose-6-kinases in germinating honey locust cotyledons: substrate specificity of D-fructo-6-kinase.
Extracts of the cotyledons of germinated honey locust (Gleditsia triacanthos) seeds, which contain galactomannan as a reserve polysaccharide in the endosperm, were fractionated by chromatography and the fractions examined for the presence of a specific manno-6-kinase which could phosphorylate the D-mannose released by hydrolysis of galactomannan. One particulate hexokinase (the major hexose-6-kinase fraction) and two soluble hexokinase fractions (the minor portion), as well as a soluble fructo-6-kinase fraction, were initially separated. From chromatography, electrophoresis and kinetic studies, no evidence for a specific manno-kinase was obtained. This and the level and kinetic behaviour of the particulate hexokinase implicated it as the enzyme catalysing the phosphorylation of released D-mannose. The fructo-kinase activity was further separated into three fractions. Kinetic studies on one of these with native and synthetic substrates indicated that the structural requirements for the monosaccharide substrate were a beta-D-anomeric 2-OH in the furanose ring, a 4-OH trans to the D-5-CH2OH and a -CH2OH substituent on C2 (trans to the 5-CH2OH) which could be modified. The orientation of the hydroxyl on C-3 had only a limited effect.
Myers
D
D
Department of Agricultural Chemistry and Soil Science, University of Sydney, NSW, Australia.
Matheson
N K
NK
D002240:Carbohydrate Sequence; D005591:Chemical Fractionation; D018548:Cotyledon / Q000201:enzymology*; D007887:Fabaceae / Q000201:enzymology*; D005631:Fructokinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D018525:Germination; D006593:Hexokinase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D007700:Kinetics; D008969:Molecular Sequence Data; D010946:Plants, Medicinal; D012995:Solubility; D013379:Substrate Specificity
D005631:Fructokinases; D006593:Hexokinase; C046173:fructokinase