Selective cleavage of glycyl bonds by papaya proteinase IV.
The specificity of papaya proteinase IV (PPIV) has been examined with small substrates and a protein. With both classes of substrate, the enzyme shows a marked selectivity for cleaving glycyl bonds. Boc-Ala-Ala-Gly-NHPhNO2 is a convenient substrate for routine assays that discriminate well against chymopapain, the most common contaminant of PPIV. Sixteen cleavage points in beta-trypsin were identified, of which 13 are glycyl bonds. Tentative suggestions are made as to the reasons for lack of cleavage of some other glycyl bonds. The structure of PPIV has been modelled on that of papain, and we suggest that the replacement of the highly conserved residues Gly-65 and Gly-23 by arginine and glutamic acid, respectively, can account for the specificity of PPIV.
Biochemistry Department, Strangeways Research Laboratory, Cambridge, England.
D J
DJ
Buttle
A
A
Ritonja
L H
LH
Pearl
V
V
Turk
A J
AJ
Barrett
D000595:Amino Acid Sequence; D001665:Binding Sites; D005638:Fruit / Q000201:enzymology*; D005998:Glycine / Q000032:analysis*; D006868:Hydrolysis; D007700:Kinetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010447:Peptide Hydrolases / Q000378:metabolism*; D013379:Substrate Specificity; D014357:Trypsin / Q000032:analysis / Q000378:metabolism*
D010447:Peptide Hydrolases; D014357:Trypsin; C030732:protease IV; D005998:Glycine