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On the role of N ‐7‐mercaptoheptanoyl‐ O ‐phospho‐L‐threonine (component B) in the enzymatic reduction of methyl‐coenzyme M to methane
Author(s) -
Ellermann J.,
Kobelt A.,
Pfaltz A.,
Thauer R.K.
Publication year - 1987
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(87)80846-3
Subject(s) - chemistry , threonine , enzyme , cofactor , methyl group , methane , stereochemistry , reductase , non competitive inhibition , biochemistry , medicinal chemistry , organic chemistry , group (periodic table) , serine
The reduction of methyl‐coenzyme M (CH 3 SCoM) to methane in methanogenic bacteria is dependent on component B ( N ‐7‐mercaptoheptanoyl‐ O ‐phospho‐L‐threonine, HSHTP). We report here that S ‐methyl‐component B ( N ‐7‐(methylthio)heptanoyl‐ O ‐phospho‐L‐threonine, CH 3 SHTP) can substitute for neither CH 3 SCoM nor HSHTP in the methyl‐CoM reductase reaction. Rather, CH 3 SHTP proved to be an inhibitor competitive with HSHTP (apparent K i =6 μM) and noncompetitive with CH 3 SCoM. These results make it very unlikely that HSHTP functions as a methyl group carrier. A role for HSHTP as direct electron donor for CH 3 SCoM reduction to CH 4 is proposed.