Department of Agricultural Chemistry, University of Sydney, N.S.W. 2006, Australia.
Plant Physiol. 1977 Nov;60(5):666-9. doi: 10.1104/pp.60.5.666.
A fructokinase (EC 2.7.1.4) was obtained from pea (Pisum sativum L.) seeds. This enzyme, termed fructokinase (fraction IV), was specific for fructose as substrate and had little activity with glucose or mannose. Excess fructose inhibited the enzyme at the optimum pH (8.2) but not at pH 6.6. MgATP was inhibitory at pH 6.6. The apparent Michaelis-Menten constants at pH 8.2 were 0.057 mm for fructose and 0.10 mm for MgATP. Mg(2+) ions were essential for activity; Mn(2+) could partially replace Mg(2+). Fructokinase (fraction IV) had a requirement for K(+) ions which could be substantially replaced by Rb(+) or NH(4) (+) but not by Na(+). The enzyme was inhibited by MgADP. The possible significance of fructokinase (fraction IV) in plant carbohydrate metabolism is discussed.
从豌豆(Pisum sativum L.)种子中获得了一种果糖激酶(EC 2.7.1.4)。该酶被称为果糖激酶(第四部分),特异性地以果糖为底物,对葡萄糖或甘露糖几乎没有活性。过量的果糖在最适 pH(8.2)下抑制酶,但在 pH 6.6 下不抑制。MgATP 在 pH 6.6 时具有抑制作用。在 pH 8.2 时,果糖和 MgATP 的表观米氏常数分别为 0.057 mm 和 0.10 mm。Mg2+离子是活性所必需的;Mn2+可以部分替代 Mg2+。果糖激酶(第四部分)需要 K+离子,Rb+或 NH4+可以大量替代,但不能用 Na+替代。该酶被 MgADP 抑制。讨论了果糖激酶(第四部分)在植物碳水化合物代谢中的可能意义。