Bromelain inhibition

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],... 

Its mechanism of action, however, is not completely elucidated. Kamakura et al. [94] studied the effects of stem bromelain on the plasma kallikrein system, bradykinin levels and plasma exudation at the inflammatory site in rats with a kaolin-induced inflammation of an air pouch. Bromelain caused a dose-dependent decrease of bradykinin levels (measured with the method of Minami et al. [95]) at the inflammatory site and a parallel decrease of the prekallikrein levels in sera [88]. Plasma exudation was also reduced dose-dependently. Bradykinin-degrading activity in sera was elevated after bromelain treatment, but not in the pouch fluid. The authors conclude that bromelain inhibits plasma exudation through inhibition of the bradykinin generation at the inflammatory site via depletion of the plasma kallikrein system. Bromelain also shows a dose-dependent analgesic effect in concanavalin A-injected paws of 5.6 mg/kg i.v.), considered to be due to decrease of high molecular weight kininogen [96]. 

Cysteine proteases are a class of enzymes that have been widely studied over the years. The overall principles of substrate recognition, catalysis, and inhibition are now reasonably well documented. This enzyme class includes the plant proteases such as papain, actinidin, and bromelain, and several mammalian lysosomal cathe-psins. By far the majority of the literature reports dealing with cysteine proteases describe results obtained with the enzyme papain, because it is considered to be the archetype of this enzyme class. 

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-... 

A potent cysteine proteinase inhibitor PCPl 8.3 was isolated from potato tubers. The inhibitor has a broad inhibitor spectrum, including the bromelain enzymes, which am not inhibited by cystatin. PCPI shows a Ki value of 190 nM for stem bromelain, 33 nM for firuit bromelain, 0.06 nM for ananain, and 3.3 nM for papain [78]. ft is proposed (hat the differences of inhibitory spectrum between PCPl and the cystatins may be those of distinct supeifamilies of cysteine proteinase inhibitors. 

The anti-inflaminatory action of bromelain preparations is the result of dif-fjrjnt mechanisms thatnft simultaneous 11. First there is, as described sbevr, the depletion of the plasma kallikrein system, inhibiting the generation of bndykinin, a known chemical mediator of inflammation. Second, there is a negative action... 

S. J, Taussig, J. SzefarcaeK, and S. Batkin. Inhibition of tumor growth in vitro by bromelain, an extract of ihc pineapple plant (Ananas camosus). rianra hied. 6 556... 

Inhibition. Since papain, ficin, and bromelain are all enzymes whose activity depends on a free SH group, it is to be expected that all thiol reagents act as inhibitors. Thus, a-halogen acids or amides and N-ethyl-maleimide irreversibly inhibit the thiol proteases. Heavy metal ions and organic mercurial salts inhibit in a fashion that can be reversed by low molecular weight thiols, particularly in the presence of EDTA which... 

It is irreversibly inhibited by 1-3 dibromoacetone, M-(4-dimethy 1 amino-3-5dinitrophenyl)maleimide, A/-ethylmaleimide, and iodoacetic acid. The chymotrypsin inhibitors W-tosyl-L-phenylalanyl-chloromethane (TPCK) and W-tosyl-L-lysylchloromethane (TLCK) alkylate the essential SH group [38]. Di-isopropylfluorophosphate (DFP) alkylates the Tyr residues of bromelain but does not react with its catalytic SH. It causes no inhibition of the caseinolytic activity, but the catalytic efficiency against BAEE is enhanced [75]. 

Human plasma inhibits the hydrolysis of casein by stem bromelain [76]. Stem bromelain is inhibited by a2-macroglobulin, but not by ai-antitiypsin [38,77]. 

Bromelain has been used as an anti-inflammatory agent and to heal edema from the time it became available as a drug [2,4-7]. More recent experimental studies demonstrate that bromelain preparations are effective in the prevention and/or inhibition of experimentally induced edema in various animals (for a review, see Ref. 87). 

Bromelain (EC 3.4.22.4) a thiol enzyme from the stems and fruit of the pineapple plant. The stem enzyme is a basic glycoprotein (M, 33,000, pi 9.55) structurally and catalytically similar to papain. B. is activated by mercaptoethanol and other SH compounds, and it is irreversibly inhibited by reagents that block SH groups. It is an endopeptidase, and it is used in protein chemistry to hydrolyse polypeptide chains into large fragments. 

Thiol enzyme. SH-enzyme an enzyme whose activity depends on the presence of a certain number of free tUol groups. T.e. are found among the hydrolases, oxidoreductases and transferases. Known T.e. are bromelain, papain, urease, various flavoenzymes, pyridine nucleotide enzymes, pyridoxal phosphate enzymes and thiolproteinases. T.e. are t ically inhibited by Sulfhydryl reagents (see). 

Bromelain has shown a wide variety of pharmacological effects in cliiucal, in vitro and in vivo studies. These effects include bum debridement, anti-inflammatory activity, prevention of epinephrine-induced pulmonary edema, smooth muscle relaxation, stimulation of muscle contractions, enhanced antibiotic absorption, immunomodulation, cancer prevention and remission, antitumor activity, ulcer prevention, sinusitis relief, appetite inhibition, shortening of labor, and enhanced excretion of fat. The precise nature of these effects (some of which are not produced by other proteases such as ficin, papain, and trypsin) is not clear. 

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