EVIDENCE FOR THE EXISTENCE OF INDEPENDENT CHLOROMETHANE-UTILIZING ANDS-ADENOSYLMETHIONINE-UTILIZING SYSTEMS FOR METHYLATION IN PHANEROCHAETE-CHRYSOSPORIUM

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.