Ficin inhibition

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... 

The reactivity of the Ru-pac complexes toward the binding of the above thio-amino acids (RSH) has been reportedly used to explore the potential role of Ru-pac complexes in the inhibition of the activity of cysteine protease (CP) (25,26) and protein tyrosine phosphatase (PTP) (28). The Ru-pac complexes were found to inhibit protease activity of the three enzymes bromalien, papain, and ficin, while azo-albumine was used as the substrate (25,26). The ability of Ru-pac complexes to inhibit CP activity was attributed to the high affinity of the ruthenium complexes toward binding the SH group in the cysteine residue of the enzymes via a rapid aqua-substitution reaction (Scheme 8). 

The inhibitor is a monomeric protein with a molecular weight of 12,500. It contains 9.3% aromatic amino acids and 50.5% polar amino acid residues but no tryptophan (Table V). It inhibits most thiol pro-teinases (cathepsin H, L, B, and C, papain, and ficin) but not serine... 

Chicken egg cystatin C consists of one peptide chain with a ca. 120 amino acid residues (Mr 12,700). The two isomers known differ in their isoelectric point (pi 5.6 and pi 6.5) and their immunological properties. This inhibitor inhibits cysteine endopeptidases such as ficin and papain. In fact, cathepsins B, H, and L and dipeptidyl peptidase I are also inhibited. 

Enzymes that hydrolyze amide and ester bonds may be divided into three classes (1) those requiring a thiol group for activity, such as papain, ficin, and other plant enzymes (2) those inhibited by diisopropylphosphorofluo-ridate (DFP), such as a-chymotrypin, trypsin, subtilisin, cholinesterase, and thrombin (3) those that require a metal ion for activity. This last class includes dipeptidases, and exopeptidases such as carboxypeptidase and leucine aminopeptidase. The metal ion is involved in the stabilization of the tetrahedral intermediate (refer to Section 4.4.1). 

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. 

In an elegant study using purified proteolytic enzymes, Ladd and Butler observed that HA inhibited carboxypeptidase A, chymotrypsin A, pronase and trypsin activities, stimulated papain, ficin and subtilo peptidase and had no effect on phaseolain and tyrosinase. HA also inhibited the activity... 

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