Papain amino acid sequence

Most of the lysosomal proteases called cathepsins are small 20- to 40-kDa glycoproteins found in all animal tissues.313 Most are cysteine proteases which function best and are most stable in the low pH reducing environment of lysosomes. They resemble papain in size, amino acid sequence, and active site structures. Papain is nonspecific but most cathepsins have definite substrate preferences. Cathepsin B is the most abundant. There are smaller amounts of related cathepsins H (an aminopeptidase)314 and L315 and still less of cathepsins C, K, and others. Cathepsin B is both an endopep-tidase and an exopeptidase.316 It acts on peptides with arginine at either Pj or P2 but also accepts bulky hydro-phobic residues in Pj and prefers tyrosine at P3.317 Cathepsin S is less stable at higher pH than other cathepsins and has a more limited tissue distribution, being especially active in the immune system.318 319... 

Hie amino acid sequence of papain was determined in 1970 by Mitchel et al. [15] (Fig. 1). It exists as an unglycosylaled polypeptide of Mr 23406 (212 amino acid residues). Papain was the first cysteine proteinase for which the three-dimensional structure was deduced from x-ray diffraction data. The... 

G, Kamphuis, J. Drentii, and E. N. Baker. Thiol protease. Comparative studies based on the high-resolution structures of papain and actinidin, and an amino acid sequence information far cathenaim B and R and stem bromelain. J. MoL BioL /62 317 (19B5). 

Figure 1 Alignment of the amino acid sequences of stem bromelain and papain. Amino adds identical for both sequences are boxed. Bioin Anaco Bromelain from Ananas comasun Papa Carpa papain from Cariea papaya. (Sequences were extracted from the SwissProt protean sequence dara base.)...

Fig. 1. Amino acid sequence and schematic structure of human cystatin C. The shaded area marks the inhibitory site for papain-like cysteine proteases, which does not overlap with the inhibitory site for mammalian legumains comprising, inter alia, the Asn39 residue. The arrow indicates the Leu68 residue, which is replaced with a Gin residue in the cerebral hemorrhage producing cystatin C variant. The asterisk marks the Pro3 residue, which is partly hydroxylated.

To establish the amino acid sequence unequivocally it is necessary to have peptides with overlapping sequences. This may be accomplished by determining the sequence of fragments obtained from treating a second aliquot of the protein with chymotrypsin. If these fragments are then treated with trypsin as a check, peptides identical to those obtained previously by successive treatment with trypsin and chymotrypsin are obtained. Other proteolytic enzymes, such as pepsin, subtilisin, and papain, with wider specificity than trypsin and chymotrypsin have proved useful in sequencing of some proteins. 

The complete amino acid sequence of papain is shown in Figure 10. The structure is based on the combined eflForts of several groups of investigators (69, 72, 79). Cysteine-25 has been identified as the active thiol... 

The amino acid 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]. Die three-dimensional structure... 

Actinidin is a cysteine protease that requires a free sulfhydryl group for activity (Arcus, 1959 McDowall, 1970). This protease is composed of 220 amino acid residues with molecular mass of 23,500 (Came and Moore, 1978). The amino acid sequence of the enzyme shows considerable homology with papain, a well-known cysteine protease in immature papaya fruit (Came and... 

Fig. 7. Comparison of amino acid sequence of cathepsin B with that of papain. The light chain of cathepsin B is from residues of 1-47 and the heavy chain is from residue of 48. (From Ref. 128).

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