Webber K O, Datta N S, Hajra A K
Arch Biochem Biophys. 1987 May 1;254(2):611-20. doi: 10.1016/0003-9861(87)90144-5.
The activities, properties, and steady-state kinetics of the five enzymes catalyzing the synthesis of 1-acyl- and 1-alkyl-sn-glycerol 3-phosphate in the cultured skin fibroblasts from Zellweger syndrome patients and normal controls were studied in detail. Judging from their Km and Vmax values, glycerol phosphate acyltransferase (EC 2.3.1.15), acyl/alkyl dihydroxyacetone phosphate reductase (EC 1.1.1.101), and acyl coenzyme A reductase (long-chain alcohol forming), appear to be affected only slightly by the absence of peroxisomes characteristic of the Zellweger syndrome. Glycerophosphate acyltransferase also showed no differences in N-ethylmaleimide sensitivity nor in inhibition by dihydroxyacetone phosphate between these cell types. Dihydroxyacetone phosphate acyltransferase (EC 2.3.1.42) and alkyl dihydroxyacetone phosphate synthase (EC 2.5.1.26) have altered activity and kinetic constants in homogenates from Zellweger syndrome fibroblasts. Dihydroxyacetone phosphate acyltransferase has similar Km (DHAP) values in both control and Zellweger syndrome cells; however, the value for the Vmax in Zellweger syndrome cells is only 6% of that found in the controls. This is interpreted as indicating that this enzyme is not defective in this disease but is simply present at a depressed level. Also, this enzyme activity has a maximum rate at pH 7.0-7.5 in the mutant cells as opposed to pH 5.4 in the controls. Acylation of dihydroxyacetone phosphate by control cell homogenate was stimulated by N-ethylmaleimide at both pH 5.7 and 7.5 whereas this activity from Zellweger syndrome cells was slightly inhibited at pH 5.7 and strongly inhibited at pH 7.5. In the absence of detergent, dihydroxyacetone phosphate acyltransferase in the Zellweger syndrome cells was much more labile to trypsin than in the control cells. Alkyl dihydroxyacetone phosphate synthase had a slightly higher Km (33 vs 17 microM) for palmitoyl dihydroxyacetone phosphate and a lower Vmax (0.07 vs 0.24 mU/mg protein) in the Zellweger syndrome cells as compared to controls. Although this is a substantial decrease in activity, it probably contributes little to the decreased rate of ether lipid synthesis in these cells. The major problem in this respect is apparently the loss of dihydroxyacetone phosphate acyltransferase activity. All of these enzymes, in both control and Zellweger syndrome cell homogenates, are sedimentable by centrifugation at 100,000g. Also, with the exception of dihydroxyacetone phosphate acyltransferase they had similar patterns of inactivation by heat in both cell types.
详细研究了来自齐尔韦格综合征患者和正常对照的培养皮肤成纤维细胞中催化1-酰基-和1-烷基-sn-甘油3-磷酸合成的五种酶的活性、性质和稳态动力学。从它们的Km和Vmax值判断,甘油磷酸酰基转移酶(EC 2.3.1.15)、酰基/烷基二羟基丙酮磷酸还原酶(EC 1.1.1.101)和酰基辅酶A还原酶(形成长链醇)似乎仅受到齐尔韦格综合征特有的过氧化物酶体缺失的轻微影响。甘油磷酸酰基转移酶在这些细胞类型之间的N-乙基马来酰亚胺敏感性或二羟基丙酮磷酸抑制方面也没有差异。二羟基丙酮磷酸酰基转移酶(EC 2.3.1.42)和烷基二羟基丙酮磷酸合酶(EC 2.5.1.26)在齐尔韦格综合征成纤维细胞的匀浆中活性和动力学常数发生了改变。二羟基丙酮磷酸酰基转移酶在对照细胞和齐尔韦格综合征细胞中的Km(二羟基丙酮磷酸)值相似;然而,齐尔韦格综合征细胞中的Vmax值仅为对照细胞中的6%。这被解释为表明该酶在这种疾病中没有缺陷,只是含量降低。此外,该酶活性在突变细胞中在pH 7.0 - 7.5时有最大速率,而在对照细胞中为pH 5.4。对照细胞匀浆中二羟基丙酮磷酸的酰化在pH 5.7和7.5时均受到N-乙基马来酰亚胺的刺激,而齐尔韦格综合征细胞的这种活性在pH 5.7时略有抑制,在pH 7.5时强烈抑制。在没有去污剂的情况下,齐尔韦格综合征细胞中的二羟基丙酮磷酸酰基转移酶比对照细胞中的对胰蛋白酶更不稳定。与对照相比,齐尔韦格综合征细胞中烷基二羟基丙酮磷酸合酶对棕榈酰二羟基丙酮磷酸的Km略高(33对17 microM),Vmax较低(0.07对0.24 mU/mg蛋白质)。尽管这是活性的显著降低,但它可能对这些细胞中醚脂合成速率的降低贡献不大。在这方面的主要问题显然是二羟基丙酮磷酸酰基转移酶活性的丧失。在对照细胞和齐尔韦格综合征细胞匀浆中,所有这些酶通过100,000g离心均可沉淀。此外,除二羟基丙酮磷酸酰基转移酶外,它们在两种细胞类型中的热失活模式相似。