Aliphatic compounds, biotic

In general, abiotic substitution reactions proceed slowly, but can be greatly accelerated by enzymes. Enzyme-mediated substitutions frequently involve cysteine residues in proteins or peptides, such as glutathione. Biotic and abiotic hydrolysis of halogenated aliphatic compounds yields alcohols by hydros l substitution at the halogenated carbon [10]. If these alcohols are themselves halogenated, further hydrolysis to acids or diols can occur. Examples of microbially-mediated hydrolysis reactions, together with responsible enzymes, are provided in Table 1. 

Methyl groups from SAM are also transferred to thiol-containing drugs and xeno-biotics. It appears that the only structural requirements are the presence of a free thiol and that the compound is not too hydrophilic in nature. S-Methylation has been demonstrated with mercaptoethanol, thioacetanilide, and 6-mercaptopurine, as well as with a variety of thiopurine and thiopyrimidine drugs. In general, aromatic thiols are the best substrates, while simple aliphatic thiols are less active. 

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