Inhomogeneity of vitamin K2 in Escherichia coli

Campbell, I.; Bentley, Ronald

doi:10.1021/bi00839a063

Cited by 12 publications

(2 citation statements)

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“…b Nanomoles per gram wet weight of cells. and Bentley, 1969) and chemically synthesized demethylmenaquinone 1 (the latter compound was kindly supplied by Dr. D. I. Magrath). To determine the concentration of menaquinone 8, the increase in absorbance at 245 nm was measured after the addition of solid sodium borohydride to a sample containing 10 mM ammonium acetate buffer (pH 5.0) (Lester et al, 1964), the increase in absorbance due to demethylmenaquinone 8 ( 19 800) was subtracted, and the concentration of menaquinone 8 ( 25 800) was calculated (Dunphy and Brodie, 1971).…”

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Alternative hydroxylases for the aerobic and anaerobic biosynthesis of ubiquinone in Escherichia coli

Alexander¹,

Young²

1978

Biochemistry

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The synthesis of ubiquinone under anaerobic conditions was examined in a variety of strains of Escherichia coli K12. All were shown to synthesize appreciable quantities of ubiquinone 8 when grown anaerobically on glycerol in the presence of fumarate. Under these conditions, ubiquinone 8 was in most cases the principal quinone formed, and levels in the range 50--70% of those obtained aerobically were observed. Studies with mutants blocked in the various reactions of the aerobic pathway for ubiquinone 8 synthesis established that under anaerobic conditions three alternative hydroxylation reactions not involving molecular oxygen are used to derive the C-4, -5, and -6 oxygens of ubiquinone 8. Thus, mutants blocked in either of the three hydroxylation reactions of the aerobic pathway (ubiB, ubiH, or ubiF) are each able to synthesize ubiquinone 8 anaerobically, whereas mutants lacking the octaprenyltransferase (ubiA), carboxy-lyase (ubiD), or methyltransferases (ubiE or ubiG) of the aerobic pathway remain blocked anaerobically. The demonstration that E. coli possesses a special mechanism for the anaerobic biosynthesis of ubiquinone suggests that this quinone may play an important role in anaerobic metabolism.

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Alternative hydroxylases for the aerobic and anaerobic biosynthesis of ubiquinone in Escherichia coli

Alexander¹,

Young²

1978

Biochemistry

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“…I. balsamina produces lawsone (2-hydroxy-l,4-naphthoquinone) and the involvement of shikimic acid as a seven-carbon unit in its biosynthesis had already been demonstrated (Leistner and Zenk, 1968). The preliminary plant experiments established conclusively that glutamate, or more likely its deamination product, 2-ketoglutarate, was indeed the source of the "missing" three carbon atoms (Campbell, 1969). As shown in Table IV, The extent of labeling of carbon atoms C-l, C-2, and C-3 of ring B was computed as described below.…”

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confidence: 98%