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Mechanism of alkylation at C-24 during ergosterol biosynthesis in Phycomyces blakesleeanus |
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| Authors: | EIan Mercer Susan M Russell |
| Institution: | Department of Biochemistry and Agricultural Biochemistry, University College of Wales, Aberystwyth, SY23 3DD U.K. |
| Abstract: | Ergosterol isolated from Phycomyces blakesleeanus grown in the presence of methionine-methyl-2H3] contained two 2H atoms showing that one 2H atom is lost during transmethylation. Ergosterol isolated from P. blakesleeanus grown in the presence of mevalonic acid-2-14C,(4R)-4-3H1] had a 14C:3H atomic ratio of 5:3. Chemical degradation of 2,3-dimethylbutanal obtained by ozonolysis of the doubly-labelled ergosterol showed that the 3H atom originally at C-24 of lanosterol is transferred to C-25 of ergosterol during transmethylation. The mechanism of formation of the ergosterol side chain in P. blakesleeanus is presented. |
| Keywords: | Mucoraceae biosynthesis ergosterol alkylation at C-24 hydrogen transfer from C-24 to C-25 The trivial names of the sterols used in the text have the following systematic names ergosterol = (24R)-24-methylcholesta-5 7 22-trien-3β-ol lanosterol = 4 4 14α-trimethyl-5α-cholesta-8 24-dien-3β-ol norcyclolaudenol = 4α 14α-dimethyl-9β 19-cyclo-5α-ergost-25-en-3β-ol episterol = 5α-ergosta-7 24(28)-dien-3β-ol 24-methylene-24 25-dihydrolanosterol = 4 4 14α-trimethyl-5α-trimethyl-5α-ergosta-8 24(28)-dien-3β-ol |
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