Thiol proteases

Additional endoproteases may be shown to play a role in neuropeptide biosynthesis. Leading candidates are the mammalian homolog of the yeast aspartyl protease-3 (YAP-3) and a thiol protease. The processing of proANF, which involves cleavage after a single Arg residue in proANF, cannot involve PCI or PC2 since there are negligible amounts of these PCs in the heart. 

CysPc Calpain-like thiol protease family E(MF)B 1(1) 14(14) ... 

J. Hempel, H. Nicholas, H. Jomvall, Thiol Proteases and Aldehyde Dehydrogenases Evolution from a Common Thioesterase Precursor , Proteins Struct., Funct., Genet. 1991,11, 176-183. 

In addition to the lack of sequence homology, ULPs have little structural homology to other DUB classes except in the active site. The structure of ULPl (see Figure 8.2) in complex with the C-terminal aldehyde of yeast SUMO (SMT3) illustrates that, like most other DUBs, ULPs are thiol proteases, utilizing a conserved catalytic triad consisting of an active-site cysteine, histidine, and aspartate [40]. 

Yamamoto, A., Tomoo, K., Doi, M, Ohishi, H., Inoue, M., Ishida, T., Yamamoto, D., Tsuboi, S., Okamoto, H., Okada, Y. (1992). Crystal structure of papain-succinyl-Gbi-Val-Val-Ala-Ala-p-nitroaniUde complex at 1.7-A resolution noncovalent binding mode of a common sequence of endogenous thiol protease inhibitors. Biochemistry 31,11305-11309. 

The surest way to inhibit an enzyme is to block the active site irreversibly by chemical reaction with some active species to form a covalent bond. Thus, iodoacetate will irreversibly inactivate thiol proteases by forming the stable carboxymethyl mercaptan. lodoacetate is of course non-selective (many other enzymes would be inactivated), toxic (many sensitive sites would be alkylated) and moreover the drug itself is unstable due to its very reactivity. 

A straightforward approach is to hunt for short polypeptides that meet the specificity requirement of an enzyme but which, because of peculiarities of the sequence, are acted upon very slowly. Such a peptide may contain unusual or chemically modified amino acids. For example, the peptide Thr-Pro-nVal-NMeLeu-Tyr-Thr (nVal=norvaline NMeLeu = N-methylleucine) is a very slow elastase substrate whose binding can be studied by X-ray diffraction and NMR spectroscopy.6 Thiol proteases are inhibited by succinyl-Gln-Val-Val-Ala-Ala-p-nitroanilide, which includes a sequence common to a number of naturally occurring peptide inhibitors called cystatins.f They are found in various animal tissues where they inhibit cysteine proteases. 

The nucleotide sequence of the ced-3 gene revealed that the Ced3 protein is closely related to the interleukin-converting enzyme ICE,149-152 which is discussed on p. 619. ICE is a member of the caspase family of thiol proteases (p. 619). At least 14 different caspases are found in the human body. Some of them... 

Ced3 C. elegans thiol protease, related to mammalian caspase9... 

In enzymes, the most common nucleophilic groups that are functional in catalysis are the serine hydroxyl—which occurs in the serine proteases, cholinesterases, esterases, lipases, and alkaline phosphatases—and the cysteine thiol—which occurs in the thiol proteases (papain, ficin, and bromelain), in glyceraldehyde 3-phosphate dehydrogenase, etc. The imidazole of histidine usually functions as an acid-base catalyst and enhances the nucleophilicity of hydroxyl and thiol groups, but it sometimes acts as a nucleophile with the phos-phoryl group in phosphate transfer (Table 2.5). 

T4 lysozyme 33,497 helix stability of 528, 529 hydrophobic core stability of 533, 544 Tanford j8 value 544, 555, 578, 582-Temperature jump 137, 138, 541 protein folding 593 Terminal transferase 408,410 Ternary complex 120 Tertiary structure 22 Theorell-Chance mechanism 120 Thermodynamic cycles 125-131 acid denaturation 516,517 alchemical steps 129 double mutant cycles 129-131, 594 mutant cycles 129 specificity 381, 383 Thermolysin 22, 30,483-486 Thiamine pyrophosphate 62, 83 - 84 Thionesters 478 Thiol proteases 473,482 TNfn3 domain O-value analysis 594 folding kinetics 552 Torsion angle 16-18 Tbs-L-phenylalanine chloromethyl ketone (TPCK) 278, 475 Transaldolase 79 Tyransducin-o 315-317 Transit time 123-125 Transition state 47-49 definition 55... 

SH (cysteine) Thiol proteases, glyceraldehyde 3-phosphate dehydrogenase Acylenzyme... 

Dalton, J.P. and Heffernan, M. (1989) Thiol proteases released in vitro by Fasciola hepatica. Molecular and Biochemical Parasitology 35, 1 51 -155. 

Khursheed, B. Rogers, J. (1989). Barley a-amylase genes and the thiol protease gene Aleurain Use of a single poly (A) addition signal associated with a conserved pentanucleotide at the cleavage site. Proceedings of the National Academy of Sciences (USA) 86, 3987-91. 

Whittier, R.F., Dean, D.A. Rogers, J.C. (1987). Nucleotide sequence analysis of a-amylase and thiol protease genes that are hormonally regulated in barley aleurone cells. Nucleic Acids Research 15, 2515-35. 

Tomato C14 C17 C19 Homology to thiol protease Heat shock Schaffer Fischer, 1988, 1990... 

Schaffer, M.A. Fischer, R.L. (1988). Analysis of mRNAs that accumulate in response to low temperature identifies a thiol protease gene in tomato. Plant Physiology 87, 431-6. 

All proteolytic enzymes described are fairly non-specific serine endoproteases, cleaving peptide chains preferentially at the carboxyl side of hydrophobic amino acid residues. The enzymes convert their substrates into small, readily soluble fragments which can be removed easily from fabrics. Only serine protease can be used in detergent formulations, as thiol proteases such as papain would be oxidized by the bleaching agents, acidic proteases are not active at common laundry conditions, and metalloproteases such as thermolysin would lose their metal cofactors because of complexation with the water-softening agents or hydroxyl ions. 

Cysteine (or thiol) proteases. The /3-thiol group is an even better nucleophile in comparison with the serine side chain thiol proteases operate under alkaline pH values as well examples include papain and bromelain. 

Pinter, M., and Friedrich, P., 1988, The calcium dependent proteolytic system calpain-calpatatin in Drosophila melanogaster, Biochem J., 253, 467-473 Pinter, M., Stierandova, A., and Friedrich, P., 1992, Purification and characterization o a Ca2 activated thiol protease from drosophila melanogaster, Biochemistry, 31, 8201-8206 Pontremoli, S., Melloni, E., Michetti, M., Salamino, F., Sparatore, B., Horecker, B., 1988, An endogenous activator of the Ca2+ -dependent proteinase of human neutrophils that increases its affinity for Ca2+, Proc. Natl. Acad. Sci., USA, 85, 1740-1743... 

G, Kamphuis, J. Drentii, and E. N. Baker. Thiol protease. Comparative studies based on the high-resolution structures of papain and actinidin, and an amino acid sequence information far cathenaim B and R and stem bromelain. J. MoL BioL /62 317 (19B5). 

K. I. Angdides and A. L. Fink- Mechanism of thiol protease catalysis detection and... 

S. Uda, M. Sasaki, and S. Ota. Immunological cross-reaction between thiol proteases of plant origin stem and fruit bromelains. J. Biochem. 73 377 (1973). 

M. Sasaki. T. Kfito, and S. lido. Antigenic determinant common to four kinds of thiol proteases of plant origin./. Biochem. (Tokyo) 74 635 (1973). 

Shaw E, Angliker H, Rauber P et al (1986) Peptidyl fluoromethyl ketones as thiol protease inhibitors. Biomed Biochim Acta 45 1397-1403... 

Hamada K, Tamai M, Yamagishi M, Ohmura S, Sawada J, Tanaka I (1978) Isolation and characterization of E-64, a new thiol protease inhibitor. Agric Biol Chem 42 523-528... 

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