Amino acid compositions cathepsin

Les.), and Couceiro, de Almeida, and Freire (1953) have localized it histo-chemically in the electrical tissue of Electwphorus electricus L. The distribution of carbonic anhydrase in several tissues of two teleosts and its inhibition in vivo by the sulfonamides have been investigated by Maetz (1953a,b). The presence of cathepsin in the stomachs of various animals including pike and trout has been established by Buchs (1954). A new advance has also been made in the comparative study of pepsin. This enzyme, previously crystallized from salmon (Norris and Elam, 1940), halibut (Eriksen, 1943), and shark (Sprissler, 1942), has now been crystallized from three species of tuna (Norris and Mathies, 1953). These interesting researches have shown that fish pepsins differ in crystal structure, amino acid composition, and specificity from swine or bovine pepsins and show a closer relationship to one another. As pointed out by Velick and Udenfriend (1953), specificity requirements toward substrates are less exacting with extracellular enzymes. 

All the lysosomal thiol proteinases described in Section II have been isolated only recently and few structural studies have been carried out. The amino acid composition of only cathepsin B has been reported and is quite similar to those of cathepsin B from human liver (75) and rat liver (19) however Ouchterlony double difPiision analysis with antiserum against rat liver cathepsin B showed no immunological cross reactivity (40). All the lysosomal enzymes examined were shown to contain carbohydrate. The 111 of Asn is a glycosylation site in rat liver cathepsin B (128) but no detailed analysis of this carbohydrate has been reported. Since human liver cathepsin H can be purified on Con A-Sepharose (12), it may also contain a carbohydrate moiety. Rat liver cathepsin H and L also bind to Con A-Sepharose. 

Amino acid composition of human cathepsin D (y-form)... 

The amino acid composition of rabbit liver cathepsin B was similar to those reported previously for the enzymes from rat (23,24), mouse (25), and human (26) liver (Table III). The amino acid compositions of rabbit liver cathepsins M and B were similar except for higher contents of serine, histidine, cysteine, and tryptophan in the former. The molecular weights, based on the results of SDS gel electrophoresis, are also similar for cathepsin M and cathepsin B. The enzymes from rabbit liver are both glycoproteins, containing 2-3 equivalents each of mannose and glucosamine, the latter presumably present as N-acetylglucosamine (unpublished observations). 

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