Acetaldehyde decreases the antitryptic activity of alpha 1-proteinase inhibitor

The trypsin-inhibiting activity of human serum is lowered upon addition of formaldehyde or acetaldehyde thereto. Acetaldehyde reacts with alpha-1-proteinase inhibitor (alpha 1-PI) to decrease its trypsin-inhibiting ability. Acetaldehyde has only a slight effect on the tryptic hydrolysis of benzoyl-DL-arginine-p-nitroanilide. It did not decrease the inhibitory activity of the Kunitz inhibitor (Aprotinin) or soybean trypsin inhibitor. Since aldehydes form covalent products with primary amines, primary amides, arginine, tyrosine, and tryptophan in protein, as well as methylene bridges thereby crosslinking functional groups, it is proposed that one or more such interactions affect alpha 1-PI activity. It is further suggested that chronically high levels of acetaldehyde, as a metabolic produce of ethanol, may be a contributory factor to the generation of pancreatitis in alcoholics by possibly lowering the effective alpha 1-PI level which is a natural protective element from proteolysis by trypsin.