sentences:  These findings indicate that active site is very discriminatory and sterically restricted.Hydrogen cyanide seems to be an uncompetitive inhibitor, combining with Schiff's base compounds formed at the active site.Addition of carbonyl compounds to the enzyme, in the presence of hydrogen cyanide, increases hydrogen cyanide's ability to inhibit acetoacetate decarboxylase, suggesting that carbonyl compounds readily form Schiff's bases at the active site.