Houghton J D, Honeybourne C L, Smith K M, Tabba H D, Jones O T
Biochem J. 1982 Nov 15;208(2):479-86. doi: 10.1042/bj2080479.
N-Methylprotoporphyrin dimethyl ester inhibits ferrochelatase in isolated membranes of Rhodopseudomonas sphaeroides at low concentrations (around 10 nm). Full inhibition developed after a short lag phase. The inhibition was non-competitive with porphyrin substrate. Addition of inhibitor to growing cultures of Rps. sphaeroides caused a decrease (near 40%) in cytochrome content and a severe inhibition of ferrochelatase; the excretion of haem into the medium by cell suspensions was also severely inhibited. The addition of N-methylprotoporphyrin dimethyl ester to suspensions of photosynthetically competent Rps. sphaeroides Ga caused excretion of Mg-protoporphyrin monomethyl ester. When added to mutants V3 and O1, magnesium divinylphaeoporphyrin a5 monomethyl ester and 2-devinyl-2-hydroxyethylphaeophorbide a were excreted, with maximum effect at around 3 microM-inhibitor in the medium. The results are interpreted to suggest that the inhibitor decreases concentration of intracellular haem, which normally controls the activity of 5-aminolaevulinate synthetase. Unregulated activity of this enzyme leads to overproduction of protoporphyrin, which is diverted to the bacteriochlorophyll pathway. Further control operates at magnesium protoporphyrin ester conversion in normal cells.
N-甲基原卟啉二甲酯在低浓度（约10纳米）时可抑制球形红假单胞菌分离膜中的亚铁螯合酶。短暂的延迟期后出现完全抑制。该抑制作用对卟啉底物是非竞争性的。向球形红假单胞菌的生长培养物中添加抑制剂会导致细胞色素含量降低（近40%），并严重抑制亚铁螯合酶；细胞悬液向培养基中排泄血红素也受到严重抑制。向具有光合活性的球形红假单胞菌Ga悬液中添加N-甲基原卟啉二甲酯会导致单甲基镁原卟啉的排泄。当添加到突变体V3和O1中时，会排泄二乙烯基镁脱镁叶绿酸a5单甲酯和2-脱二乙烯基-2-羟乙基脱镁叶绿酸a，培养基中抑制剂浓度约为3微摩尔时效果最佳。结果表明，该抑制剂会降低细胞内血红素的浓度，而血红素通常控制着5-氨基乙酰丙酸合成酶的活性。该酶不受调节的活性会导致原卟啉过量产生，原卟啉会转向细菌叶绿素合成途径。正常细胞中，在镁原卟啉酯转化过程中还存在进一步的调控作用。
