Department of Biochemistry, University of California, Berkeley, California 94720.
Plant Physiol. 1972 Jun;49(6):977-81. doi: 10.1104/pp.49.6.977.
l-Glutamine d-fructose 6-phosphate amidotransferase (EC 2.6.1.16) was extracted and purified 600-fold by acetone fractionation and diethylaminoethyl cellulose column chromatography from mung bean seeds (Phaseolus aureus). The partially purified enzyme was highly specific for l-glutamine as an amide nitrogen donor, and l-asparagine could not replace it. The enzyme showed a pH optimum in the range of 6.2 to 6.7 in phosphate buffer. Km values of 3.8 mm and 0.5 mm were obtained for d-fructose 6-phosphate and l-glutamine, respectively. The enzyme was competitively inhibited with respect to d-fructose 6-phosphate by uridine diphosphate-N-acetyl-d-glucosamine which had a Ki value of 13 mum. Upon removal of l-glutamine and its replacement by d-fructose 6-phosphate and storage over liquid nitrogen, the enzyme was completely desensitized to inhibition by uridine diphosphate-N-acetyl-d-glucosamine. This indicates that the inhibitor site is distinct from the catalytic site and that uridine diphosphate-N-acetyl-d-glucosamine acts as a feedback inhibitor of the enzyme.
l-谷氨酸-果糖 6-磷酸酰胺基转移酶（EC 2.6.1.16）从绿豆种子（Phaseolus aureus）中通过丙酮分级和二乙基氨基乙基纤维素柱色谱法提取和纯化了 600 倍。部分纯化的酶对 l-谷氨酸作为酰胺氮供体具有高度特异性，而 l-天冬酰胺不能替代它。该酶在磷酸盐缓冲液中显示出 6.2 到 6.7 的 pH 最佳范围。对于 d-果糖 6-磷酸和 l-谷氨酸，Km 值分别为 3.8mm 和 0.5mm。该酶对尿苷二磷酸-N-乙酰-d-葡萄糖胺具有竞争性抑制作用，Ki 值为 13μm。除去 l-谷氨酸并用 d-果糖 6-磷酸代替并在液氮中储存后，该酶对尿苷二磷酸-N-乙酰-d-葡萄糖胺的抑制作用完全丧失敏感性。这表明抑制剂结合位点与催化位点不同，并且尿苷二磷酸-N-乙酰-d-葡萄糖胺是该酶的反馈抑制剂。
