Glycyl endopeptidase

G lycosyltransferases See specific enzymes GLYCYL ENDOPEPTIDASE GLYCYL-tRNA SYNTHETASE GLYOXALASE I GLYOXALASE II... 

Glycosyltransferase(s) 184, 526, 604,608 catalytic groups, table 603 Glycyl endopeptidase 618 Glycylglycine... 

Jacquct et al. described the proteolytic specificities of chymopapain and papaya proteinase Q [36]. The polypeptide chain of caricain contains 216 amino acid residues (Mr 23283). The molecule shares 148 identical amino acid residues (68,5ft) with papain. 141 with chymopapain (65,2ft), and 175 with glycyl endopeptidase (81.0ft). The Ms,lllOnin is 1U [20]. The three-dimensional structure of caricain has been determined by x-ray diffraction analysis [37,38]-... 

The amino add sequence of glycyl endopeptidase was published by Ritonja et al. [45] (Fig. 1). The enzyme exists as a single unglycosylated polypeptide of 216 amino add residues (Mr 23.313). Glycyl endopeptidase is clearly a member of the papain family of cysteine proteinases [46], The three-dimensional structure... 

Hie Si sub site has no binding pocket as such and has a much less clearly defined specificity, expect for glycyl endopeptidase. Low molecular weight substrates indicate some preference for Lys or Arg (over Ala) at P] of papain [3], Schechter and Beiger [68] showed that Leu and Phe bind equally well at Sit indicating that the interaction is probably mainly hydrophobic. It is striking, however, that Aftl is not accepted in Si [49]. 

In glycyl end (peptidase, however) the Gly-23 and Gly-65 of papain an replaced by Oiu and Aqg, respectively [45]. These residiies are located on the side walls of the active site cleft and can thus stericaly hinder the interactions al the Si subsite, which is oily accessible for Gly in glycyl endopeptidase. The absolute requirement for L-amino acids al Pi arises from the tact that when a peptide binds to the enzyme the hydrogen on the a-carbon points toward the enzyme On the vicinity of Gly-23) [63]. This is probably the reason why Domino adds cannot bind property (their side chain would clash with Gly-23) and why Gly is always conserved in position 23. 

B, P. O Hara, A. M. Hemmings, D. J. Buttle, and L. H. Pearl- Crystal structure of glycyl endopeptidase from Carica papaya a cysteine endopeptidaae of unusual sub-mate specificity. Biochemistry34 13190 (1995). 

To date, the latex of Carica papaya L. is known to contain at least four different proteolytic enzymes, namely, papain (E.C. 3.4.22.2), chymopapain (E.C. 3.4.22.6), caricain or papaya proteinase III or 2 (E.C. 3.4.22.30), and glycyl endopeptidase or papaya proteinase IV (E.C. 3.4.22.25). The importance of the latex of the unripe fruit of the tropical tree Carica papaya L. was first noted by G. C. Roy, who in 1873 published in the Calcutta Medical Journal (see Ref. 1) an article entitled The solvent action of papaya juice on the nitrogenous articles of food. The name papain was used for the first time by Wurtz and Bouchet [2] to describe partially purified cysteine proteinases from the papaya latex. They wrote, nous designerons ce ferment sous le nom de papa ine." In 1880, Wurtz postulated that papain acts in fibrin digestion by becoming bound to the fibrin [3]. This is remarkable in that Emil Fisher first described the specific association of enzyme with substrate in 1898. Since that time, many names have been used for commercial latex products, e.g., papayotin, papaoid, etc. 

The residues in the S2 subsite that make the most intimate contact are those of Val-133, Val-157, Ala-160, Pro-68, and Tyr-67. In the four enzymes of the papaya latex, all these groups remain hydrophobic, with the exception of Pro-68, which is replaced by Glu in chymopapain and in glycyl endopeptidase. The nonpolar character, and generally specificity, of the S2 subsite would therefore be conserved. 

H, K, L and O, the dipeptidyl peptidase I, and glycyl endopeptidase. The C2 family contains various calpains, whereas streptopain belongs, to CIO ubiquitin C-terminal hydrolyse PGP 9,5 to C12, and the isopeptidase T to C19. 

However, sometimes very simple derivatives can afford protection against enzymatic degradation. Thus the V-acetyl derivative of Z-glycyl-prolylamide (Figure 41.8) is six times more resistant to gut prolyl endopeptidase (which normally hydrolyzes the terminal primary amide) than the non-acetylated parent molecule. ... 

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