EVIDENCE FOR THE EXISTENCE OF INDEPENDENT CHLOROMETHANE-UTILIZING ANDS-ADENOSYLMETHIONINE-UTILIZING SYSTEMS FOR METHYLATION IN PHANEROCHAETE-CHRYSOSPORIUM
C. Coulter et al., EVIDENCE FOR THE EXISTENCE OF INDEPENDENT CHLOROMETHANE-UTILIZING ANDS-ADENOSYLMETHIONINE-UTILIZING SYSTEMS FOR METHYLATION IN PHANEROCHAETE-CHRYSOSPORIUM, Applied and environmental microbiology, 59(5), 1993, pp. 1461-1466
O methylation of acetovanillone at 4 position by (CH3Cl)-H-2 and S-ade
nosyl[methyl-H-2(3)]methionine was monitored in whole mycelia of Phane
rochaete chrysosporium in the presence and absence of S-adenosylhomocy
steine. Both the amount of the methylation product, 3,4-dimethoxyaceto
phenone, and the percent (CH3)-H-2 incorporation into the 4-methoxyl g
roup of the compound were determined. The results strongly suggest the
presence of biochemically distinct systems for O methylation of aceto
vanillone utilizing S-adenosylmethionine and chloromethane, respective
ly, as the methyl donor. The S-adenosylmethionine-dependent enzyme is
induced early in the growth cycle, with activity attaining an initial
maximum after 55 h of incubation. Methylation by this enzyme is totall
y suppressed by 1 mM S-adenosylhomocysteine over almost the entire gro
wth cycle. S-Adenosylmethionine-dependent O-methyltransferase activity
is detectable in cell extracts, and the purification and characteriza
tion of the enzyme are described elsewhere (C. Coulter, J. T. Kennedy,
W. C. McRoberts, and D. B. Harper, Appl. Environ. Microbiol. 59:706-7
11, 1993). The chloromethane-utilizing methylation system is absent in
early growth but attains peak activity in the mid-growth phase after
72 h of incubation. The system is not significantly inhibited by S-ade
nosylhomocysteine at any stage of growth. No chloromethane-dependent O
-methyltransferase activity is detectable in cell extract, suggesting
that the enzyme is membrane bound and/or part of a multienzyme complex
. Although the biochemical role of the chloromethane-dependent methyla
tion system in metabolism is not known, one possible function could be
the regeneration of veratryl alcohol degraded by the attack of lignin
peroxidase.