Patulin Biosynthesis: The Metabolism of m‐Hydroxybenzyl Alcohol and m‐Hydroxybenzaldehyde by Particulate Preparations from Penicillium patulum

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Abstract
The ring hydroxylation of m‐hydroxybenzyl alcohol to gentisyl alcohol by a particulate preparation from Penicillium patulum has been characterised. The activity was shown to be closely associated with, but not necessarily identical to, m‐cresol 2‐hydroxylase activity of the 105 000 x g microsomal fraction. As with both the m‐cresol hydroxylases of this system, m‐hydroxybenzyl alcohol hydroxylase requires oxygen and NADPH for activity. A Km value for m‐hydroxybenzyl alcohol of 15 μM was measured. Inhibition of the hydroxylase activity and its reversal by light, as well as the action of cytochrome c, KCN and other effectors suggested a mixed‐function oxidase reaction of the cytochrome P‐450, NADPH‐cytochrome reductase type. m‐Hydroxybenzaldehyde was not ring hydroxylated by any preparation from P. patulum. Apart from the previously described conversion to m‐hydroxybenzyl alcohol by a predominantly soluble dehydrogenase, m‐hydroxybenzaldehyde was metabolized to m‐hydroxybenzoic acid by a particulate fraction. This activity required NADPH. It was concluded that the main biosynthetic pathway to patulin must be through m‐hydroxybenzyl alcohol, gentisyl alcohol and gentisaldehyde.