Author/Editor		Buttle, DJ; Ritonja, A; Pearl, LH; Turk, V; Barrett, AJ
Title		Selective cleavage of glycyl bonds by papaya proteinase IV
Type		članek
Source		FEBS Lett
Vol. and No.		Letnik 260, št. 2
Publication year		1990
Volume		str. 195-7
Language		eng
Abstract		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.
Descriptors		FRUIT GLYCINE PEPTIDE HYDROLASES TRYPSIN AMINO ACID SEQUENCE BINDING SITES HYDROLYSIS KINETICS MODELS, MOLECULAR MOLECULAR SEQUENCE DATA SUBSTRATE SPECIFICITY TRYPSIN