Senda K, Yoshioka H, Doke N, Kawakita K
Plant Pathology Laboratory, School of Agricultural Sciences, Nagoya University, Japan.
Plant Cell Physiol. 1996 Apr;37(3):347-53. doi: 10.1093/oxfordjournals.pcp.a028952.
Phospholipase (PL) A2 is involved in signal transduction in the resistance reaction that is induced in potato by inoculation of an incompatible race of Phytophthora infestans, the late blight fungus, or by treatment with fungal elicitor hyphal wall components (Kawakita et al. 1993). In this study, PLA2 in the soluble fraction from potato tuber was purified. The following results suggested that the enzyme was, in fact, patatin: (1) the molecular mass of the purified enzyme was 40 kDa, the same as that of patatin; (2) the pI of the purified enzyme was approximately 4.75, which corresponds to that of patatin; and (3) the amino-terminal amino acid sequence of the purified enzyme showed a high degree of homology to that of patatin. Patatin is known as a storage protein of the potato tuber and it has been shown to have esterase activity. However, other enzymatic activities and the function(s) of patatin are unknown. We investigated the PLA activities of the purified patatin. The PLA2 activity of the patatin was much higher than the PLA1 activity, even though the protein exhibited both activities. The PLA2 activity of the enzyme was particularly apparent when phosphatidylcholine with linoleic acid at the sn-2 position was used as substrate. Lower activity was observed with phosphatidylcholine with palmitic acid, oleic acid and arachidonic acid at the sn-2 position.
磷脂酶（PL）A2参与马铃薯对致病疫霉（晚疫病真菌）不亲和小种接种或真菌激发子菌丝壁成分处理诱导的抗性反应中的信号转导（Kawakita等人，1993年）。在本研究中，对马铃薯块茎可溶性部分中的PLA2进行了纯化。以下结果表明该酶实际上是马铃薯块茎储藏蛋白：（1）纯化酶的分子量为40 kDa，与马铃薯块茎储藏蛋白相同；（2）纯化酶的pI约为4.75，与马铃薯块茎储藏蛋白的pI相对应；（3）纯化酶的氨基末端氨基酸序列与马铃薯块茎储藏蛋白的氨基末端氨基酸序列具有高度同源性。马铃薯块茎储藏蛋白是已知的马铃薯块茎储藏蛋白，已证明其具有酯酶活性。然而，马铃薯块茎储藏蛋白的其他酶活性和功能尚不清楚。我们研究了纯化的马铃薯块茎储藏蛋白的PLA活性。尽管该蛋白同时具有两种活性，但其PLA2活性远高于PLA1活性。当以sn-2位含亚油酸的磷脂酰胆碱为底物时，该酶的PLA2活性尤为明显。当以sn-2位含棕榈酸、油酸和花生四烯酸的磷脂酰胆碱为底物时，观察到较低的活性。
