Characterization of the pineapple stem proteases (bromelains).

The two major acidic sulfhydryl proteases, bromelain A and bromelain B, from the pineapple stem have been characterized by their kinetic properties toward p-nitrophenyl esters of N-α-acyl amino acids. Both enzymes show the same broad specificity toward the amino acid side chains at pH 4.7. Less than an order of magnitude of difference is observed in the rates of bromelain A-catalyzed hydrolyses of the following five amino acid esters: Z-l-lysine (kcat = 7.4 s−1, Km = 57 μM), Z-l-alanine (kcat = 2.5 s−1, Km = 24 μm), Z-l-tyrosine (kcat = 0.4 s−1, Km = 7.6 μm), Z-glycine (kcat = 1.75 s−1, Km = 174μm) and Z-l-asparagine (kcat = 1.5 s−1, Km = 75 μm). Valine, leucine, isoleucine, and tryptophan derivatives react at least one-thousand times slower. The pineapple stem acetone powder also contains sulfhydryl proteases of markedly different specificity. A purification procedure of bromelain A and B is described which eliminates these enzymatic impurities.