| Abstract [eng] |
The catabolism of alkylpyrazines is poorly described. The pathways for the degradation of di- and tri-substituted pyrazines have been proposed, but these related routes consistently include a hydroxylation step that cannot be performed on tetramethylpyrazine. Here we describe for the first time the catabolic pathway of tetramethylpyrazine in tetramethylpyrazine-degrading Rhodococcus jostii TMP1 strain. MS/MS analysis of the protein primarily upregulated by tetramethylpyrazine led to the identification of the gene locus encoding proteins required for the initial steps of tetrametylpyrazine degradation and for the regulation of this locus. Tetramethylpyrazine degradation starts with oxidative ring cleavage catalysed by monooxygenase TpdAB, which produces (Z)-N,N'-(but-2-ene-2,3-diyl)diacetamide. This compound is further hydrolysed by amidase TpdC to N-(3-oxobutan-2-yl)acetamide. TpdE was confirmed to be an aminoalcohol dehydrogenase yielding N-(3-hydroxybutan-2-yl)acetamide. By determining intermediates, enzymes involved and genes responsible for tetramethylpyrazine degradation we provide the first validated pathway for pyrazine degradation. We also report that Rhodococcus jostii TMP1 is capable of modifying various alkylpyrazines and alkylpyridines and can be employed for the bioconversion of 2,4,6-trimethylpyridine and 2,4,6-trimethylpyridin-3-ol biosynthesis. |
