Department of Biological Sciences, University of Illinois at Chicago, 845 West Taylor St., 60607-7060, Chicago, IL, USA.
Photosynth Res. 1995 Feb;43(2):125-30. doi: 10.1007/BF00042969.
Light activation of NADP-linked glyceraldehyde-3-P dehydrogenase involves reductive cleavage of a disulfide bond. We have proposed that the inactivating disulfide locks the two domains of the enzyme, preventing catalysis, and we have tentatively identified the two critical cysteine residues in the chloroplast enzyme (D. Li, F.J. Stevens, M. Schiffer and L.E. Anderson (1994) Biophys J. 67: 29-35). We reasoned that if activation of this enzyme involves these cysteines that enzymes lacking one or both should be active in the dark and insensitive to reductants. One of these cysteines is present in the enzymes from Anabaena variabilis and Synechocystis PCC 6803 but the other is not. Consistent with the proposed mechanism, glyceraldehyde-3-P dehydrogenase is not affected by DTT-treatment in extracts of either of these cyanobacteria. Fructosebisphosphatase is DTT-activated in extracts of both of these cyanobacteria and glucose-6-P dehydrogenase is inactivated in Synechocystis, as in higher plant chloroplasts. Apparently reductive modulation is possible in these cyanobacteria but glyceraldehyde-3-P dehydrogenase is not light activated.
光激活 NADP 连接的甘油醛-3-P 脱氢酶涉及二硫键的还原裂解。我们提出，失活的二硫键锁定了酶的两个结构域，阻止了催化作用，并且我们暂定鉴定了叶绿体酶中的两个关键半胱氨酸残基（D. Li、F.J. Stevens、M. Schiffer 和 L.E. Anderson（1994）生物物理学杂志 67：29-35）。我们推断，如果这种酶的激活涉及这些半胱氨酸，那么缺乏一个或两个半胱氨酸的酶应该在黑暗中活跃并且对还原剂不敏感。这些半胱氨酸之一存在于鱼腥藻和集胞藻 PCC 6803 的酶中，但另一个不存在。与提出的机制一致，DTT 处理不会影响这些蓝藻提取物中的甘油醛-3-P 脱氢酶。果糖-1,6-二磷酸酶在这两种蓝藻的提取物中均被 DTT 激活，而葡萄糖-6-P 脱氢酶在集胞藻中失活，与高等植物叶绿体中一样。显然，这些蓝藻中可能存在还原调节，但甘油醛-3-P 脱氢酶不会被光激活。
