Bovine placental protease specificity toward muscle connective tissue proteins

Enzymes currently used to tenderize meat are not substrate-specific, result ing in extensive myofibrillar protein degradation that often produces an un desirable texture. Bovine placental metalloproteases, which selectively hyd rolyze connective tissue proteins while leaving myofibrillar proteins intac t, may tenderize meat without causing texture problems. Therefore, our obje ctive was to extract and crudely purify bovine metalloproteases from bovine placenta for possible use as tenderizers in meat systems. Enzymes were ext racted from homogenized tissue and purified by ammonium sulfate precipitati on. Samples were collected before (crude enzyme) and after gel filtration o n a Sephadex G-100 column. Spectrophotometric analysis identified one major peak (filtered enzyme). Gelatin, casein, and type I acid-soluble collagen zymography were used to determine substrate specificity. Beef myofibrillar proteins were incubated with crude and filtered enzyme fractions, enzymes q uenched, and substrate degradation visualized using SDS-PAGE. Active gelati nases and collagenases exhibiting molecular weights of 57 to 65 kDa were de tected on zymograms. Banding patterns from crude enzyme indicated two enzym es with both gelatinase and collagenase activity and a third; enzyme with g elatinase activity only. Banding patterns from filtered enzyme indicated tw o enzymes with both gelatinase and collagenase activity. Proteolytic activi ty was not detected with casein, actin, or myosin heavy-chain substrates. D ue to specificity for collagen and gelatin, these enzymes may be capable of improving the tenderness of certain cuts relatively high in connective tis sue, while avoiding myofibrillar protein hydrolysis.