Imaoka S, Terano Y, Funae Y
Laboratory of Chemistry, Osaka City University Medical School, Japan.
Arch Biochem Biophys. 1990 Apr;278(1):168-78. doi: 10.1016/0003-9861(90)90245-t.
The effects of starvation on the composition of 12 different cytochrome P450s in rat hepatic microsomes were studied with a specific antibody. Changes in the metabolic activity of the microsomes were studied at the same time. P450 DM (P450j) was induced 2.5-fold by a 48-h starvation and its increase reflected the increase of metabolic activity of hepatic microsomes toward aniline, 7-ethoxycoumarin, and N-nitrosodimethylamine. P450 K-5, the major renal cytochrome P450 in untreated male rat, was also induced 2.5-fold by a 48-h starvation. P450 UT-2 (P450h) and P450 UT-5 (P450g), typical male-specific forms, decreased with starvation. P450 UT-2 had high testosterone 2 alpha- and 16 alpha-hydroxylation activities. These activities of hepatic microsomes were reduced with the decrease in P450 UT-2. P450 PB-1, testosterone 6 beta-hydroxylase, was increased time-dependently by starvation. P450 UT-4 (RLM2), a minor male-specific form, was not changed by starvation. P450 PB-2 (P450k), present in both sexes, was changed little by starvation. P450 PB-4 (P450b) and P450 PB-5 (P450e) are strongly induced in rat liver by phenobarbital in coordinate fashion. Starvation increased P450 PB-4 12-fold but reduced P450 PB-5 to 22% of the control level. P450 MC-1 (P450d) was decreased by starvation. P450 MC-5 (P450c) was barely detected in control rats and was not changed by starvation. P450 IF-3 (P450a), rich in immature rats, was increased by starvation, accompanied by an increase in testosterone 7 alpha-hydroxylation activity in the hepatic microsomes. We further investigated whether new cytochrome P450s appeared upon starvation by comparison of chromatographic profiles of cytochrome P450 from starved rats with those of cytochrome P450 from control rats using HPLC. Three new cytochrome P450s were detected in the starved rats. These cytochrome P450s were purified to homogeneity. One of them was P450 DM, judging from spectral properties, catalytic activity, and the NH2-terminal sequence. The two other forms were designated P450 3b and 4b. The minimum molecular weights of P450 3b and 4b were 53,000 and 52,000, respectively, and their CO-reduced absorption maxima were at 449 and 452 nm, respectively. P450 3b metabolized aminopyrine, N-nitrosodimethylamine, 7-ethoxycoumarin, and lauric acid, but with low activity. P450 4b was efficient in lauric acid omega- and (omega-1)-hydroxylation only. The spectral properties, catalytic activity, peptide map, and NH2-terminal sequence of P450 4b agreed with those of P450 K-5. P450 3b was a new cytochrome P450, judged by these criteria.
用特异性抗体研究了饥饿对大鼠肝微粒体中12种不同细胞色素P450组成的影响。同时研究了微粒体代谢活性的变化。48小时饥饿诱导P450 DM（P450j）增加2.5倍，其增加反映了肝微粒体对苯胺、7-乙氧基香豆素和N-亚硝基二甲胺代谢活性的增加。未处理的雄性大鼠主要的肾细胞色素P450，P450 K-5，也被48小时饥饿诱导增加2.5倍。P450 UT-2（P450h）和P450 UT-5（P450g），典型的雄性特异性形式，随饥饿而减少。P450 UT-2具有高的睾酮2α-和16α-羟化活性。随着P450 UT-2的减少，肝微粒体的这些活性降低。睾酮6β-羟化酶P450 PB-1随饥饿呈时间依赖性增加。P450 UT-4（RLM2），一种次要的雄性特异性形式，不受饥饿影响。两性均存在的P450 PB-2（P450k），受饥饿影响很小。苯巴比妥以协同方式强烈诱导大鼠肝脏中的P450 PB-4（P450b）和P450 PB-5（P450e）。饥饿使P450 PB-4增加12倍，但使P450 PB-5降至对照水平的22%。饥饿使P450 MC-1（P450d）减少。对照大鼠中几乎检测不到P450 MC-5（P450c），且其不受饥饿影响。富含未成熟大鼠的P450 IF-3（P450a），随饥饿增加，同时肝微粒体中睾酮7α-羟化活性增加。我们通过使用高效液相色谱法比较饥饿大鼠与对照大鼠细胞色素P450的色谱图谱，进一步研究了饥饿时是否出现新的细胞色素P450。在饥饿大鼠中检测到三种新的细胞色素P450。这些细胞色素P450被纯化至均一。根据光谱特性、催化活性和氨基末端序列判断，其中一种是P450 DM。另外两种形式分别命名为P450 3b和4b。P450 3b和4b的最小分子量分别为53,000和52,000，其一氧化碳还原吸收最大值分别在449和452 nm。P450 3b代谢氨基比林、N-亚硝基二甲胺、7-乙氧基香豆素和月桂酸，但活性较低。P450 4b仅对月桂酸ω-和（ω-1）-羟化有效。P450 4b的光谱特性、催化活性、肽图和氨基末端序列与P450 K-5一致。根据这些标准判断，P450 3b是一种新的细胞色素P450。
