Yamaguchi J, Nishimura M, Akazawa T
Eur J Biochem. 1986 Sep 1;159(2):315-22. doi: 10.1111/j.1432-1033.1986.tb09870.x.
In germinating pumpkin seeds, catalase is synthesized as a precursor (59-kDa) form, with molecular mass larger than the mature molecule (55 kDa). Both the precursor and mature forms of catalase are localized in the microbodies, i.e., glyoxysomes and leaf peroxisomes [Proc. Natl. Acad. Sci. USA 81, 4809-4813 (1984)]. We have now purified the 59-kDa catalase precursor and compared its properties with those of the 55-kDa mature molecule. The molar catalytic activity of the 59-kDa catalase was tenfold lower than that of the 55-kDa molecule, whereas the heme content was found to be same, with both forms containing four hematin groups per molecule. It is inferred from these results that the low activity of the 59-kDa molecule is not related to the binding of heme to the protein, but presumably involves conformational differences between the 59-kDa and 55-kDa molecules. We have further found that the reduction of total catalase activity in pumpkin cotyledons during greening was due to a decrease in the amount of the enzymically active 55-kDa catalase accompanying an increase in the 59-kDa molecule.
在发芽的南瓜种子中，过氧化氢酶以一种前体（59 kDa）形式合成，其分子量大于成熟分子（55 kDa）。过氧化氢酶的前体和成熟形式都定位于微体中，即乙醛酸循环体和叶片过氧化物酶体[《美国国家科学院院刊》81, 4809 - 4813 (1984)]。我们现在已经纯化了59 kDa的过氧化氢酶前体，并将其性质与55 kDa成熟分子的性质进行了比较。59 kDa过氧化氢酶的摩尔催化活性比55 kDa分子低10倍，而血红素含量相同，两种形式每分子都含有四个血红素基团。从这些结果可以推断，59 kDa分子的低活性与血红素与蛋白质的结合无关，而可能涉及59 kDa和55 kDa分子之间的构象差异。我们还进一步发现，南瓜子叶在变绿过程中总过氧化氢酶活性的降低是由于随着59 kDa分子的增加，具有酶活性的55 kDa过氧化氢酶的量减少所致。
