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A classical enzyme active center motif lacks catalytic competence until modulated electrostatically.
The cysteine proteinase superfamily is a source of natural structural variants of value in the investigation of mechanism. It has long been considered axiomatic that catalytic competence of these
A reporter group delivery system with both absolute and selective specificity for thiol groups and an improved fluorescent probe containing the 7-nitrobenzo-2-oxa-1,3-diazole moiety.
TLDR
Spectral analysis of the reactions of compound (I) with L-cysteine and with papain showed that even under equimolar conditions the reaction is essentially stoicheimoetric and probably proceeds by specific attack at the sulphur atom distal from the pyridyl ring of compounds (I).
The activity of the tissue inhibitors of metalloproteinases is regulated by C-terminal domain interactions: a kinetic analysis of the inhibition of gelatinase A.
TLDR
The C-terminal peptide of TIMP-2 is proposed to exist as an exposed "tail" responsible for binding to progelatinase A and for increasing the rate of inhibition of active gelatinase A through electrostatic interactions with the C-Terminal domain of the enzyme.
Comparative studies on the 5-aminolaevulinic acid dehydratases from Pisum sativum, Escherichia coli and Saccharomyces cerevisiae.
TLDR
The crystallization of the yeast ALAD is described, raising the possibility of an X-ray-derived three-dimensional structure of this enzyme.
Demonstration that 1-trans-epoxysuccinyl-L-leucylamido-(4-guanidino) butane (E-64) is one of the most effective low Mr inhibitors of trypsin-catalysed hydrolysis. Characterization by kinetic analysis
1-trans-Epoxysuccinyl-L-leucylamido(4-guanidino)butane (E-64) was shown to inhibit beta-trypsin by a reversible competitive mechanism; this contrasts with the widely held view that E-64 is a
Structural insights into substrate specificity and the anti beta-elimination mechanism of pectate lyase.
TLDR
It is clear that the catalytic calcium ions and adjacent lysine promote catalysis by acidifying the alpha-proton, facilitating its abstraction by the base.
Mechanism of the reaction of papain with substrate-derived diazomethyl ketones. Implications for the difference in site specificity of halomethyl ketones for serine proteinases and cysteine
TLDR
Existing data are shown to suggest an interpretation involving neighbouring-group participation via transient thiohemiketal formation, rate-determining protonation by imidazolium ion and alkylation on sulphur via a three-membered cyclic transition state in the mechanism of papain-catalysed hydrolysis.
Reactions of papain and of low-molecular-weight thiols with some aromatic disulphides. 2,2'-Dipyridyl disulphide as a convenient active-site titrant for papain even in the presence of other thiols.
TLDR
The rates of these reactions are considerably faster at pH8 than at pH4, which suggests that the predominant reaction pathway in approximately neutral media is nucleophilic attack of the thiolate ion on the unprotonated disulphide.
Characterization of retinaldehyde dehydrogenase 3.
TLDR
Analogies with data for non-phosphorylating glyceraldehyde-3-Phosphate dehydrogenase from Streptococcus mutans suggest that kcat characterizes deacylation of this intermediate for specific substrates and the assignment of the pKa of the major ionization to the perturbed carboxy group of Glu280 whose conjugate base is envisaged as supplying general base catalysis to attack of a water molecule.
A necessary modification to the preparation of papain from any high-quality latex of Carica papaya and evidence for the structural integrity of the enzyme produced by traditional methods.
A method of preparation of papain (EC 3.4.22.2) from relatively soluble types of latex of Carica papaya, including spray-dried latex produced by a controlled and relatively mild process, was devised.
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