Intracellular animal proteases active at acid pH have been extensively studied (for a review see refs
[ 1,2] ), and these studies have led to the identification, separation and at least partial characterization of a number of enzymes involved.
Proteolytic activity
at neutral pH in animal tissue extracts, on the other hand, has often been mentioned, but reports on the isolation, separation or characterization of the enzymes are scarce ([3-8] , and others).
This is partly due to the much higher activities at acid pH values, but also to the rather elusive nature of the enzyme(s) assumed to be active at neutral pH.
We directed our studies to the proteolytic activity possibly present in beef spleen, and especially to the problem of the existence of an endopeptidase active at neutral or slightly alkaline pH values. For the detection of this activity the traditional Kunitz method [9] using the absorbancy increase at 280 nm with casein as substrate, is hazardous [lo].
We, therefore,
used more sensitive and specific methods, viz. the
Folin-reagent [ 11,121 and the ninhydrin method (13)
Intracellular animal proteases active at acid pH have been extensively studied (for a review see refs[ 1,2] ), and these studies have led to the identification, separation and at least partial characterization of a number of enzymes involved.Proteolytic activityat neutral pH in animal tissue extracts, on the other hand, has often been mentioned, but reports on the isolation, separation or characterization of the enzymes are scarce ([3-8] , and others).This is partly due to the much higher activities at acid pH values, but also to the rather elusive nature of the enzyme(s) assumed to be active at neutral pH.We directed our studies to the proteolytic activity possibly present in beef spleen, and especially to the problem of the existence of an endopeptidase active at neutral or slightly alkaline pH values. For the detection of this activity the traditional Kunitz method [9] using the absorbancy increase at 280 nm with casein as substrate, is hazardous [lo].We, therefore,used more sensitive and specific methods, viz. theFolin-reagent [ 11,121 and the ninhydrin method (13)
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