Lichko L P, Kulakovskaya T V, Kulaev I S
Skryabin Institute of Biochemistry and Physiology of Microorganisms, Russian Academy of Sciences, Pushchino 142290, Moscow Region, Russia.
Biochemistry (Mosc). 2004 Mar;69(3):270-4. doi: 10.1023/b:biry.0000022056.00041.c3.
Inactivation of PPX1 encoding the major cytosolic exopolyphosphatase PPX1 in Saccharomyces cerevisiae did not alter exopolyphosphatase activity of the isolated nuclei compared with that in the parent strain. The nuclear exopolyphosphatase of the S. cerevisiae strain deficient in the PPX1 gene was purified 10-fold. According to gel filtration on Superose 6, this enzyme has a molecular mass of approximately 200 kD, and it hydrolyzes polyphosphates with an average chain length of 15 and 208 phosphate residues to the same extent. Its activity is much lower with tripolyphosphate. In the presence of 2.5 mM Mg2+, Km values are 133 and 25 microM in the hydrolysis of polyphosphates with chain lengths of 15 and 208 phosphate residues, respectively. The enzyme activity is stimulated by 2.5 mM Mg2+ and 0.1 mM Co2+ 15- and 31-fold, respectively. RNA does not alter the nuclear exopolyphosphatase activity, while polylysine increases it 2-fold.
与亲本菌株相比，酿酒酵母中编码主要胞质外切多聚磷酸酶PPX1的PPX1失活并未改变分离细胞核的外切多聚磷酸酶活性。PPX1基因缺陷的酿酒酵母菌株的细胞核外切多聚磷酸酶被纯化了10倍。根据Superose 6凝胶过滤结果，该酶的分子量约为200 kD，它对平均链长为15和208个磷酸残基的多聚磷酸的水解程度相同。它对三聚磷酸的活性要低得多。在2.5 mM Mg2+存在下，水解链长为15和208个磷酸残基的多聚磷酸时，Km值分别为133和25 microM。该酶的活性分别受到2.5 mM Mg2+和0.1 mM Co2+的刺激，提高了15倍和31倍。RNA不会改变细胞核外切多聚磷酸酶的活性，而聚赖氨酸会使其活性提高2倍。
