HUMAN PANCREATIC ISLETS EXPRESS MRNA SPECIES ENCODING

一种命名为iPLA 2的85 kDa VI组磷脂酶A2酶， 不需要Ca 2+的催化作用最近被克隆， 三种啮齿动物 一个同源的88 kDa的酶已被克隆 来自人B淋巴细胞系，其含有54个氨基酸的插入物， 存在于啮齿类动物的酶中，但人类细胞以前没有 已经观察到表达催化活性iPLA 2同种型， 88 kDa的蛋白质。 我们已经克隆了编码两种 来自人胰岛RNA的不同iPLA 2同种型和来自人胰岛RNA的不同iPLA 2同种型。 胰岛素瘤cDNA文库。 一种同种型是85 kDa蛋白（SH-iPLA 2） 另一个为88 kDa蛋白（LH-iPLA 2）。 转录本编码 在人前单核细胞U937细胞中也观察到同种型。 重组SH-iPLA 2和LH-iPLA 2均具有催化活性， 缺乏Ca 2+，并被溴烯醇内酯（BEL）自杀抑制 LH-iPLA 2被ATP激活，而SH-iPLA 2不被ATP激活。 人类iPLA 2基因已被发现位于22号染色体上， 区域q13.1，并含有LH-iPLA 2中代表的16个外显子 成绩单。 外显子8不存在于SH-iPLA 2转录物中， 这表明它是通过选择性的外显子跳跃机制产生的。 拼接 由人源性大肠杆菌的外显子8编码的氨基酸序列， iPLA 2基因富含脯氨酸，共有一个共有基序， Px 5 Px 8HHPx 12 Nx 4 Q与富含脯氨酸的中间接头结构域 Smad蛋白α-3和Smad 4。 mRNA种类编码的表达 两种活性iPLA 2同种型，具有不同的催化特性， 这里展示的两种不同类型的人类细胞可能具有 产品作用的监管或功能影响 iPLA 2基因在细胞生物学过程中的作用。

An 85 kDa Group VI phospholipase A2 enzyme, designated iPLA2, that does not require Ca2+ for catalysis has recently been cloned from three rodent species. An homologous 88 kDa enzyme has been cloned from human B-lymphocyte lines that contains a 54 amino acid insert not present in the rodent enzymes, but human cells have not previously been observed to express catalytically active iPLA2 isoforms other than the 88 kDa protein. We have cloned cDNA species that encode two distinct iPLA2 isoforms from human pancreatic islet RNA and a human insulinoma cDNA library. One isoform is an 85 kDa protein (SH-iPLA2) and the other an 88 kDa protein (LH-iPLA2). Transcripts encoding both isoforms are also observed in human promonocytic U937 cells. Recombinant SH-iPLA2 and LH-iPLA2 are both catalytically active in the absence of Ca2+ and inhibited by a bromoenol lactone (BEL) suicide substrate, but LH-iPLA2 is activated by ATP, while SH-iPLA2 is not. The human iPLA2 gene has been fou nd to resi de on chromosome 22 in region q13.1 and to contain sixteen exons represented in the LH-iPLA2 transcript. Exon 8 is not represented in the SH-iPLA2 transcript, indicating that it arises by an exon-skipping mechanism of alternative splicing. The amino acid sequence encoded by exon 8 of the human iPLA2 gene is proline-rich and shares a consensus motif of Px5Px8HHPx12Nx4Q with the proline-rich middle linker domains of the Smad proteins DAF-3 and Smad4. Expression of mRNA species encoding two active iPLA2 isoforms with distinguishable catalytic properties in two different types of human cells demonstrated here may have regulatory or functional implications about the roles of products of the iPLA2 gene in cell biologic processes.