Boles E, Schulte F, Miosga T, Freidel K, Schlüter E, Zimmermann F K, Hollenberg C P, Heinisch J J
Institut für Mikrobiologie, Heinrich-Heine-Universität, Düsseldorf, Germany.
J Bacteriol. 1997 May;179(9):2987-93. doi: 10.1128/jb.179.9.2987-2993.1997.
We have characterized the gene YOR347c of Saccharomyces cerevisiae and shown that it encodes a second functional pyruvate kinase isoenzyme, Pyk2p. Overexpression of the YOR347c/PYK2 gene on a multicopy vector restored growth on glucose of a yeast pyruvate kinase 1 (pyk1) mutant strain and could completely substitute for the PYK1-encoded enzymatic activity. PYK2 gene expression is subject to glucose repression. A pyk2 deletion mutant had no obvious growth phenotypes under various conditions, but the growth defects of a pyk1 pyk2 double-deletion strain were even more pronounced than those of a pyk1 single-mutation strain. Pyk2p is active without fructose-1,6-bisphosphate. However, overexpression of PYK2 during growth on ethanol did not cause any of the deleterious effects expected from a futile cycling between pyruvate and phosphoenolpyruvate. The results indicate that the PYK2-encoded pyruvate kinase may be used under conditions of very low glycolytic flux.
我们已经对酿酒酵母的YOR347c基因进行了表征，并表明它编码第二种功能性丙酮酸激酶同工酶Pyk2p。在多拷贝载体上过量表达YOR347c/PYK2基因可恢复酵母丙酮酸激酶1（pyk1）突变株在葡萄糖上的生长，并可完全替代PYK1编码的酶活性。PYK2基因的表达受到葡萄糖抑制。pyk2缺失突变体在各种条件下没有明显的生长表型，但pyk1 pyk2双缺失菌株的生长缺陷比pyk1单突变菌株更明显。Pyk2p在没有果糖-1,6-二磷酸的情况下具有活性。然而，在乙醇上生长期间过量表达PYK2并没有引起丙酮酸和磷酸烯醇丙酮酸之间无效循环所预期的任何有害影响。结果表明，PYK2编码的丙酮酸激酶可能在糖酵解通量非常低的条件下发挥作用。
