Boddupalli S S, Pramanik B C, Slaughter C A, Estabrook R W, Peterson J A
Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas.
Arch Biochem Biophys. 1992 Jan;292(1):20-8. doi: 10.1016/0003-9861(92)90045-x.
The soluble P450 isolated from Bacillus megaterium (the product of the CYP 102 gene) (P450BM-3) is a catalytically self-sufficient fatty acid hydroxylase which converts lauric, myristic, and palmitic acids to omega-1, omega-2, and omega-3 hydroxy analogs. The percentage distribution of the regioisomers depends on the substrate chain length. Lauric and myristic acids were preferentially metabolized to their omega-1 hydroxy counterparts while no hydroxylation occurred when capric acid was used as the substrate. Palmitic acid, when present at concentrations greater than the concentration of oxygen in the reaction medium (greater than 250 microM), was hydroxylated to its omega-1, omega-2, and omega-3 hydroxy analogs, with the percentage distribution of the regioisomers being 21:44:35, respectively. No omega hydroxylation of any of the fatty acids was detected. When the concentration of palmitic acid was less than the concentration of oxygen in the reaction mixture, it was noted that a number of additional products were formed. Under these conditions, unlike lauric and myristic acids, it was observed that palmitic acid was first converted to its monohydroxy isomers which were subsequently metabolized to a mixture of 14-ketohexadecanoic, 15-ketohexadecanoic, 13-hydroxy-14-ketohexadecanoic, 14-hydroxy-15-ketohexadecanoic, and 13,14-dihydroxyhexadecanoic acids with a relative distribution of 8:2:40:30:20, respectively. Thus, P450BM-3 is able not only to monohydroxylate a variety of fatty acids but also to further metabolize some of these primary metabolites to secondary and tertiary products. The present paper characterizes the products formed during the sequential hydroxylation of palmitic acid and proposes reaction pathways to explain these results.
从巨大芽孢杆菌中分离出的可溶性细胞色素P450（CYP 102基因的产物）（P450BM-3）是一种具有催化自足性的脂肪酸羟化酶，可将月桂酸、肉豆蔻酸和棕榈酸转化为ω-1、ω-2和ω-3羟基类似物。区域异构体的百分比分布取决于底物链长。月桂酸和肉豆蔻酸优先代谢为其ω-1羟基对应物，而当癸酸用作底物时则不发生羟基化。当棕榈酸的浓度高于反应介质中的氧气浓度（大于250μM）时，它会被羟基化为其ω-1、ω-2和ω-3羟基类似物，区域异构体的百分比分布分别为21:44:35。未检测到任何脂肪酸的ω-羟基化。当棕榈酸的浓度低于反应混合物中的氧气浓度时，注意到形成了许多其他产物。在这些条件下，与月桂酸和肉豆蔻酸不同，观察到棕榈酸首先转化为其一羟基异构体，随后这些异构体被代谢为14-酮十六烷酸、15-酮十六烷酸、13-羟基-14-酮十六烷酸、14-羟基-15-酮十六烷酸和13,14-二羟基十六烷酸的混合物，相对分布分别为8:2:40:30:20。因此，P450BM-3不仅能够将多种脂肪酸单羟基化，还能够将其中一些初级代谢产物进一步代谢为二级和三级产物。本文对棕榈酸连续羟基化过程中形成的产物进行了表征，并提出了反应途径来解释这些结果。
