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首页> 外文期刊>The Biochemical Journal >Pyridoxine biosynthesis in yeast: participation of ribose 5-phosphate ketol-isomerase
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Pyridoxine biosynthesis in yeast: participation of ribose 5-phosphate ketol-isomerase

机译：酵母中吡rid醇的生物合成：核糖5-磷酸酮醇异构酶的参与

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摘要

To identify the genes involved in pyridoxine synthesis in yeast, auxotrophic mutants were prepared. After transformation with a yeast genomic library, a transformant (A22tl) was obtained from one of the auxotrophs. A22, which lost the pyridoxine auxotrophy. From an analysis of the plasmid harboured in A22tl the RKII gene coding for ribose 5-phosphate ketol-isomerase and residing on chromosome no. 15 was identified as the responsible gene. This notion was confirmed by gene disruption and tetrad analysis on a diploid prepared from the wild-type and the auxotroph. The site Of Mutation on the RKII gene was identified as position 566 with a transition from guanine to adenine, resulting in amino acid Substitution of Arg-189 with lysine. The enzymic activity of the Arg(189) --> Lys (R189K) Mutant of ribose 5-phosphate ketolisomerase was 0.6 % when compared with the wild-type enzyme. Loss of the structural integrity of the protein seems to be responsible for the greatly diminished activity, which eventually leads to a shortage of either ribose 5-phosphate or ribulose 5-phosphate as the starting or intermediary material for pyridoxine synthesis.
机译：为了鉴定涉及酵母中吡ido醇合成的基因，制备了营养缺陷型突变体。用酵母基因组文库转化后，从营养缺陷型之一获得转化体（A22tl）。 A22，它失去了吡x醇营养缺陷型。从对A22t1中携带的质粒的分析来看，RKII基因编码核糖5-磷酸酮醇异构酶，并位于第5号染色体上。 15个被鉴定为负责任基因。通过对野生型和营养缺陷型制备的二倍体进行基因破坏和四联体分析，证实了这一观点。 RKII基因上的突变位点被鉴定为位置566，具有从鸟嘌呤到腺嘌呤的转变，从而导致赖氨酸取代了Arg-189的氨基酸。与野生型酶相比，核糖5-磷酸核糖异构酶的Arg（189）-> Lys（R189K）突变体的酶活性为0.6％。蛋白质结构完整性的丧失似乎是造成活性大大降低的原因，这最终导致了核糖5-磷酸或核糖5-磷酸作为吡ido醇合成的起始或中间材料的短缺。

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