Bromelain substrate specificity

Stem bromelain has a broad substrate specificity, dose to the specificity of ficin (EC 3.4.22.3), end hydrolyzes a great variety of synthetic and natural substrates. It preferentially cleaves peptide bonds when a hydrophobic group is in the rz position. (According to Scheduler and Betger [32], the amino add residues in a substrate undergoing cleavage are designated as Pi, P2, P3, etc. in the N-tennmal direction and Pi, Y P3r, etc. in the C-temunal direction from the cleaved bond.) Predominantly Gly-Fhe, Phe-Ser, Tyr-Ile, and "iyr-Val bands are cleaved [33,34]. The specificity of bromelain is different from that of papain and ficin in that it hydrolyzes most effectively derivatives of Lys, Ala, T r, Gly, and Asn [35]. 

For historical reasons many pharmaceutical enzymes are assayed with physiological or biopolymeric substrates (proteins, polysaccharides, bacteria, oil emulsions), which causes a number of theoretical and practical problems. The interpretation of results is difficult when natural substrates are converted into products that are substrates themselves for the next enzymatic attack. Reaction rates often depend on the position of the scissile bonds in the molecule and the chemical nature of the moieties. Hydrolysis can proceed simultaneously on various bonds at various rates. In proteolysis it is assumed that some products are liberated only after denaturation and that during the reaction course new peptide bonds become accessible for hydrolysis. In these cases the enzymatic mechanisms become exceedingly complex, kinetic parameters are apparent values, and experimental results are strongly influenced by the reaction conditions. Reproducibility problems can occur upon assaying proteinases with a limited specificity for particular casein types. Bromelain and pancreatic proteinase, FEP pharmaceutical enzyme standards, are assayed with a casein substrate. The extent of soluble peptide release is a measure of proteolytic activity. However, due to limited specificity, some proteinases release peptides with a nonrandom aromatic amino acid composition. Contamination of casein preparations with protein and of test enzyme substances with other proteinases biases the assay results. Under these conditions, relative assay methods are indicated. 

Like papain, stem bromelain has broad specificity, hydrolyzing various proteinaceous substrates (e.g., proteins, amides, esters, and small peptides). 

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