Model experiments in our laboratory have given support for a reaction mechanism of this type; eg, t-butyl alcohol and succinic acid are formed in the reaction between t-butyl hydroperoxide and a-ketoglutarate. To establish that molecular oxygen is incorporated into succinate in the enzyme reaction, as required by the above mechanism, we have carried out the hydroxylation of y-butyrobetaine in an lsOz-enriched atmosphere.