Bromelain active cysteine

His1 0 and orients it for its catalytic function [54], The putative catalytic thiolate-imldazollum pair at the active site of bromelain is thus, by comparison of the amino acid sequence of bromelain with other cysteine protein ases, likely to have a different conformation from that in (he cysteine proteinases (hat aie tightly inhibited by cystatin [45]. Bromelain also distinguishes itself from other cysteine protein ases by its slow inhibition by the irreversible inhibitor of cysteine oroteinases E-64 rW-ft 3-fraw-cari)OKVOxiran-2 BrboiwlVL-leucvn-amido 4-... 

Bromelain is a mixture of cysteine proteases obtained from pineapple stems (Ananas comosus, Bromeliaceae) that has been used therapeutically for the treatment of inflammation and trauma [119]. 7n vitro, it has varied stimulatory effects on leukocyte populations, increases CD2-mediated T cell activation, enhances Ag-independent binding to monocytes, etc. The effects of bromelain have previously been attributed to its degradative action at cell surfaces. However, it also acts independent of the removal of cell surface molecules [120]. In order to investigate the possible hormonelike effects of bromelain on intracellular signalling, its effects on TCR7CD3 signalling and IL-2 production were studied. It was observed that bromelain inhibits ERK-2 activation in ThO cells stimulated via the TCR, or with combined TPA plus calcium ionophore. In addtion, bromelain decreased IL-2, IFN-y, and IL-4 mRNA accumulation in ThO cells stimulated with TPA plus calcium ionophore, while the cytokine mRNA accumulation in cells stimulated via TCR was not affected. It seems that bromelain does not act on ERK-2 directly but also inhibits p2r activation, an effector molecule upstream from ERK-2 in the Raf-1/MEKl/ERK kinase cascade. Since p21 is an effector for multiple MAPK pathways, it is likely that bromelain affects other MAPK signalling cascades, such as the INK pathway or p38 MAPK pathway [121],... 

For soluble and immobilized bromelain, temperature increase is accompanied by a decrease in residual enzyme activity. A more complex form of denaturation occurs with the immobilized enzyme, which may involve a two-phase process. Immobilization offers more resistance to denaturation at the higher temperature of 60°C where the second phase is prolonged by a factor of three [60]. Differential scanning calorimetry experiments showed that bromelain is an exceptional protease among the cysteine proteases, illustrated by the fact that its thermal denaturation is consistent with an irreversible two-state model [61]. Also, the far UV circular dichroism spectrum of bromelain differs from those of papain and chymopapain and therefore represents a third spectral class within the cysteine proteinase family [62],... 

S. S. Hussain and G. Lowe. The amino acid sequence around the active-site cysteine and histidine residues of stem bromelain. Biochem. J. 7/7 341 (1970). 

Albumin binds OPs on tyrosine 411 of human albumin or tyrosine 410 of bovine albumin (Sakurai ei aL, 2004), The adjacent arginine residue activates this tyrosine for reaction with esters as well as with OPs. Other non-serinc hydrolases that react with OPs include papain and bromelain, which are cysteine proteases that stochiometrically bind OPs on tyrosine, without loss of protease activity (Murachi. 1963 Chaiken and Smith, 1969). 

Cysteine endopeptidase Cysteine in the active site Papain, ficin, bromelain, cathepsin B... 

An exceptionally reactive serine residue has been identified in a great number of hydrolase enzymes, e. g., trypsin, subtilisin, elastase, acetylcholine esterase and some lipases. These enzymes appear to hydrolyze their substrates by a mechanism analogous to that of chymotrypsin. Hydrolases such as papain, ficin and bromelain, which are distributed in plants, have a cysteine residue instead of an active serine residue in their active sites. Thus, the transient intermediates are thioesters. 

Corresponding equations were derived for the cysteine proteases ficin, actinidin, bromelain B and D, and the serine proteases subtilisin, chymotrypsin, and trypsin. In all cases, the coefficient of the electronic a term is around 0.4-0.7. Whereas the other regression coefficients in equations (16) and (17) are also relatively similar, the constant terms of both equations differ by about 1.8 log units, which indicates that the lower lipophilicity of the mesyl group, as compared with a much more lipophilic benzoyl group, is responsible for the lower binding affinities of the mesyl amides. To prove this hypothesis, a series of (4-X-Phe)-CONHCH2COO-pyrid-3-yl analogs 12 was synthesized and tested. As expected, lipophilicity determines the structure-activity relationship in this part of the molecules (equation IS). " " ... 

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