一种迄今未知的转酮醇酶催化反应。
A hitherto unknown transketolase-catalyzed reaction.
作者信息
Sevostyanova Irina A, Solovjeva Olga N, Kochetov German A
机构信息
ANBelozersky Institute of Physico-Chemical Biology, Moscow State University, 119992 Moscow, GSP-2, Russia.
出版信息
Biochem Biophys Res Commun. 2004 Jan 16;313(3):771-4. doi: 10.1016/j.bbrc.2003.11.164.
Yeast transketolase, in addition to catalyzing the transferase reaction through utilization of two substrates--the donor substrate (ketose) and the acceptor substrate (aldose)--is also able to catalyze a one-substrate reaction with only aldose (glycolaldehyde) as substrate. The interaction of glycolaldehyde with holotransketolase results in formation of the transketolase reaction intermediate, dihydroxyethyl-thiamin diphosphate. Then the glycolaldehyde residue is transferred from dihydroxyethyl-thiamin diphosphate to free glycolaldehyde. As a result, the one-substrate transketolase reaction product, erythrulose, is formed. The specific activity of transketolase was found to be 0.23 U/mg and the apparent Km for glycolaldehyde was estimated as 140 mM.
酵母转酮醇酶，除了通过利用两种底物——供体底物（酮糖）和受体底物（醛糖）来催化转移酶反应外，还能够催化仅以醛糖（乙醇醛）作为底物的单底物反应。乙醇醛与全酶转酮醇酶的相互作用导致转酮醇酶反应中间体二羟乙基硫胺素二磷酸的形成。然后，乙醇醛残基从二羟乙基硫胺素二磷酸转移至游离的乙醇醛。结果，形成了单底物转酮醇酶反应产物赤藓酮糖。发现转酮醇酶的比活性为0.23 U/mg，乙醇醛的表观Km估计为140 mM。
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