Tanaka Y, Takahashi M, Kawaguchi M, Amano F
Department of Biochemistry and Cell Biology, National Institute of Health, Tokyo, Japan.
Biol Pharm Bull. 1997 Apr;20(4):322-6. doi: 10.1248/bpb.20.322.
In a mouse macrophage-like cell line, RAW264.7, arachidonic acid was cleaved within 30 min of lipopolysaccharide (LPS)-treatment. However, prostaglandin (PG) synthesis did not accompany this cleavage, being delayed by 4 h, although significant PGH synthase (PGHS) activity was detected in the lysate of LPS-nontreated cells. The K(m) value of this basal PGHS activity toward arachidonic acid was more than one hundred-fold higher than that for the lysate of cells treated with LPS for 4 h. Changes in the sensitivity of the PGHS activity to nonsteroidal antinflammatory drugs after LPS-treatment also suggested induction of PGHS with different properties from that in the case of basal PGHS. The concomitant increase in PGH synthase (PGHS) activity with the induction of PGHS-2 protein after LPS-treatment suggested a contribution by PGHS-2 to the delayed synthesis of PGs in LPS-treated macrophage cells. As for PGHS in the control cells without LPS-treatment, a different K(m) value from that of PGHS-1 and the lack of cross-reactivity to anti-PGHS-1 antibodies suggested that this basal PGHS was different from the typical PGHS-1. The lower affinity of this enzyme for arachidonic acid might be the reason for the failure to release PGs by the cells without LPS-treatment.
在小鼠巨噬细胞样细胞系RAW264.7中，脂多糖（LPS）处理后30分钟内花生四烯酸被裂解。然而，前列腺素（PG）合成并未伴随这种裂解，而是延迟了4小时，尽管在未用LPS处理的细胞裂解物中检测到了显著的前列腺素H合成酶（PGHS）活性。这种基础PGHS活性对花生四烯酸的米氏常数（K(m)）比用LPS处理4小时的细胞裂解物的米氏常数高一百多倍。LPS处理后PGHS活性对非甾体抗炎药敏感性的变化也表明诱导产生了与基础PGHS性质不同的PGHS。LPS处理后PGH合成酶（PGHS）活性与PGHS-2蛋白诱导的同时增加表明PGHS-2对LPS处理的巨噬细胞中PG的延迟合成有贡献。对于未用LPS处理的对照细胞中的PGHS，其米氏常数与PGHS-1不同，且与抗PGHS-1抗体缺乏交叉反应，这表明这种基础PGHS与典型的PGHS-1不同。这种酶对花生四烯酸的亲和力较低可能是未用LPS处理的细胞未能释放PG的原因。
