Corcuera L J, Michalczuk L, Bandurski R S
Biochem J. 1982 Nov 1;207(2):283-90. doi: 10.1042/bj2070283.
Extracts of immature kernels of Zea mays catalysed the synthesis of indol-3-ylacetyl-myo-inositol galactoside from indol-3-ylacetyl-myo-inositol and UDP-galactose. Addition of 2-mercaptoethanol was required for stability of the catalytic activity during dialysis. The enzyme could be fractionated with (NH4)2SO4, and 55% of the activity was recovered in the 30-60%-saturation fraction. The product of the reaction contained radioactivity from UDP-[U-14C]galactose and was identified as indol-3-ylacetyl-myo-inositol galactoside by gas chromatography-mass spectrometry. Therefore a UDP-galactose:indol-3-ylacetyl-myo-inositol galactosyltransferase (indol-3-ylacetyl-myo-inositol galactoside synthase) is present in developing kernels of Zea mays. The description of this enzyme, together with the enzymes described in the accompanying paper [Michalczuk & Bandurski (1982) Biochem. J. 207, 273-281] for the synthesis of indol-3-ylacetylglucose and indol-3-ylacetyl-myo-inositol, now provides mechanisms for the biosynthesis of one-half of the low-molecular-weight esters of indol-3-ylacetic acid in Zea mays.
玉米未成熟籽粒的提取物催化了吲哚 - 3 - 基乙酰 - 肌醇半乳糖苷从吲哚 - 3 - 基乙酰 - 肌醇和UDP - 半乳糖的合成。透析过程中，为保持催化活性的稳定性需要添加2 - 巯基乙醇。该酶可用硫酸铵分级分离，55%的活性在饱和度为30% - 60%的级分中得以回收。反应产物含有来自UDP - [U - 14C]半乳糖的放射性，通过气相色谱 - 质谱法鉴定为吲哚 - 3 - 基乙酰 - 肌醇半乳糖苷。因此，在玉米发育中的籽粒中存在一种UDP - 半乳糖：吲哚 - 3 - 基乙酰 - 肌醇半乳糖基转移酶（吲哚 - 3 - 基乙酰 - 肌醇半乳糖苷合酶）。对该酶的描述，连同随附论文[Michalczuk & Bandurski (1982) Biochem. J. 207, 273 - 281]中描述的用于合成吲哚 - 3 - 基乙酰葡萄糖和吲哚 - 3 - 基乙酰 - 肌醇的酶，现在为玉米中吲哚 - 3 - 基乙酸低分子量酯一半的生物合成提供了机制。
