methanol gets converted to formaldehyde in the liver by an enzyme called alcohol dehydrogenase. This is an oxidative reaction requiring the cofactor NAD+ which gets converted (reduced) to NADH. The reaction can also occur without alcohol dehydrogenase in microsome of a cell. In this case cytochrome P4502E1 is the enzyme and the redox agent is NADPH which gets converted (oxidized) to NADP.