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首页> 美国卫生研究院文献>Biochemical Journal >Frog brain uridine diphosphate galactose–N-acetylgalactosaminyl-N-acetylneuraminylgalactosylglucosylceramide galactosyltransferase
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Frog brain uridine diphosphate galactose–N-acetylgalactosaminyl-N-acetylneuraminylgalactosylglucosylceramide galactosyltransferase

机译：青蛙脑尿苷二磷酸半乳糖–N-乙酰半乳糖胺基-N-乙酰神经氨酸基半乳糖基葡萄糖基神经酰胺半乳糖基转移酶

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1. The enzyme that catalyses the transfer of galactose from UDP-galactose to N-acetylgalactosaminyl-(1→4)-N-acetylneuraminyl-(2→3)-galactosyl-(1→4)-glucosylceramide (GM2) was found mainly in the heavy- and light-microsomal fractions of the adult frog brain. 2. The subcellular distribution of the enzyme, UDP-galactose–GM2 galactosyltransferase, parallels that of gangliosides in adult frog brain. 3. The enzymic activity was first detected at late gastrulation (Shumway stage 11½) and increased until the completion of the operculum (Shumway stage 25) and then decreased in the tadpoles. 4. In adult frog brain, the enzyme exhibited a pH optimum of 7.2–7.3 in both cacodylate and tris buffers. The enzyme required 10mm-Mn2+ for maximal activity and the Km for Mn2+ was determined as 2.2mm. The half-maximal velocity was obtained at a GM2 concentration of 0.18mm. Inhibition of the enzymic reaction was found when the GM2 concentration was greater than 1.38mm. 5. The enzymic activity was also inhibited by the products in the pathway of ganglioside synthesis, i.e. either by a mixture of gangliosides or by individual ganglioside components. The most active inhibitor was disialoganglioside. The degree of inhibition is a function of the individual ganglioside concentration. 6. A product-inhibition mechanism for the regulation of ganglioside biosynthesis is discussed.
机译：1.主要发现了催化半乳糖从UDP-半乳糖转移至N-乙酰半乳糖胺基-（1→4）-N-乙酰神经氨酸-（2→3）-半乳糖基-（1→4）-葡萄糖基神经酰胺（GM2）的酶在成年蛙脑的重微粒体和轻微粒体中2.该酶的UDP-半乳糖–GM2半乳糖基转移酶的亚细胞分布与成年蛙脑中神经节苷脂的分布相似。 3.首先在后期胃化阶段（舒马威阶段11½）检测到酶活性，并增加直到the盖完成（舒马威阶段25），然后在t中降低。 4.在成年蛙脑中，该酶在草酸和tris缓冲液中的最适pH值为7.2–7.3。该酶需要10mm-Mn 2 + 才能发挥最大活性，而Mn 2 + 的Km被确定为2.2mm。在GM2浓度为0.18mm时获得了最大速度的一半。当GM2浓度大于1.38mm时，发现酶反应被抑制。 5.神经节苷脂合成途径中的产物，即神经节苷脂的混合物或单个神经节苷脂组分也抑制了酶活性。活性最高的抑制剂是双唾液酸神经节苷脂。抑制程度是各个神经节苷脂浓度的函数。 6.讨论了调节神经节苷脂生物合成的产物抑制机制。

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