Guaiacol can't be produced from catechol, ferulic acid, phenylalanine and tyrosine.
Vanillin was reduced to vanillyl alcohol by NADPH-dependent vanillin reductase.
Vanillin was oxidized to vanillic acid by NAD(P)+-linked vanillin dehydrogenases.
The vanillic acid decarboxylase was inducible, reversible and oxygen insensitive.