豌豆种子的果糖激酶（组分III）
Fructokinase (Fraction III) of Pea Seeds.
作者信息
Copeland L, Harrison D D, Turner J F
机构信息
Department of Agricultural Chemistry, University of Sydney, N.S.W. 2006, Australia.
出版信息
Plant Physiol. 1978 Aug;62(2):291-4. doi: 10.1104/pp.62.2.291.
A second fructokinase (EC 2.7.1.4) was obtained from pea seed (Pisum sativum L. var. Progress No. 9) extracts. The enzyme, termed fructokinase (fraction III), was specific for fructose and had little activity with glucose. With fructose concentrations above 0.25 millimolar, there was strong substrate inhibition at the optimum pH (8.0) and also at pH 6.6. The apparent K(m) values at pH 8.0 for fructose and glucose were 0.06 millimolar and 0.14 millimolar, respectively. The apparent K(m) for Mg adenosine 5'-triphosphate (MgATP) was 0.06 millimolar and excess MgATP was inhibitory. Mg(2+) was essential for activity but the enzyme was inhibited by excess Mg(2+) or ATP. Mg adenosine 5'-pyrophosphate was also inhibitory. Activity was stimulated by the addition of monovalent cations: of those tested K(+), Rb(+), and NH(4) (+) were the most effective. The possible role of fructokinase (fraction III) is discussed.
第二种果糖激酶（EC 2.7.1.4）是从豌豆种子（豌豆品种Progress No. 9）提取物中获得的。该酶被称为果糖激酶（组分III），对果糖具有特异性，对葡萄糖的活性很低。当果糖浓度高于0.25毫摩尔时，在最佳pH值（8.0）以及pH 6.6时均存在强烈的底物抑制作用。在pH 8.0时，果糖和葡萄糖的表观K(m)值分别为0.06毫摩尔和0.14毫摩尔。镁腺苷5'-三磷酸（MgATP）的表观K(m)为0.06毫摩尔，过量的MgATP具有抑制作用。Mg(2+)对活性至关重要，但过量的Mg(2+)或ATP会抑制该酶。镁腺苷5'-焦磷酸也具有抑制作用。添加单价阳离子可刺激活性：在所测试的阳离子中，K(+)、Rb(+)和NH(4) (+)最为有效。文中讨论了果糖激酶（组分III）可能的作用。
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