COMPARATIVE OXIDATION OF 2-PROPYN-1-OL WITH OTHER LOW-MOLECULAR-WEIGHT UNSATURATED AND SATURATED PRIMARY ALCOHOLS BY BOVINE LIVER CATALASE IN-VITRO

The oxidative metabolism of low molecular weight, saturated and unsatu rated, primary alcohols, which include ethanol, allyl alcohol (2-prope n-1-ol), and propargyl alcohol (2-propyn-1-ol), is generally accepted to occur via alcohol dehydrogenase; however, compared to other short-c hain alcohols, 2-propyn-1-ol is a poor substrate for this enzyme. Acco rdingly, we have examined liver catalase as an alternative pathway for the oxidation or bioactivation of 2-propyn-1-ol to 2-propyn-1-al, a h ighly reactive cr,p-unsaturated aldehyde. The rates of oxidation for a series of low molecular weight, saturated, primary alcohols and selec ted unsaturated alcohols were determined for the bovine liver catalase -catalyzed reaction by measuring aldehyde production over time employi ng a GC procedure. A negative correlation was found for log rates of o xidation versus molecular size (volume) of the substrates (p < 0.01); however, the rate of oxidation for 2-propyn-1-ol was higher than predi cted by this relation and was 30% greater than the oxidation rate dete rmined for ethanol. In addition, 2-propyn-1-ol-derived 2-propyn-1-al i nhibited the peroxidatic and catalatic activities of catalase, whereas 2-propen-1-ol-derived 2-propen-1-al had no effect on these activities of catalase. Inhibition was blocked by GSH; and the activity was not restored to the inhibited enzyme by GSH treatment or dialysis. These f indings support the hypothesis that oxidative conversion of 2-propyn-1 -ol to the more reactive 2-propyn-1-al by liver catalase is the initia l step in 2-propyn-1-ol-induced liver injury; however, alternative oxi dative pathways for alcohol metabolism have not been completely exclud ed from this process.