Proteinases protein turnover

E. Shaw, R. T. Dean The inhibition of macrophage protein turnover by a selective inhibitor of thiol proteinases. Biochem J 1980, 186, 385-390. 

Okitani, A., Goll, D., Stromer, M., Robson, R., Intracellular inhibitor of a Ca2+-dependent proteinase involved in myofibrillar protein turnover, Federation Proc., 35, 1746 Ono, Y., Sorimachi, H., Suzulu, K., 2004, Structure, Activation, and Biology of Calpain, Biochem. 

The inhibition of sporulation by netropsin, an antibiotic interacting with AT groups in the chromosome and suppressing the synthesis of several enzymes related to sporulation [13,14], caused an Inhibition of protein turnover but stimulated the rate of exocellular proteinase formation [15], Netropsin not only increased the synthesis of the enzyme at the beginning of incubation in sporulation medium but delayed also its late suppression (Table 1), It must be stated, however, that the antibiotic stimulated the proteinase formation also during growth and its effect thus does not seem to be specific for sporulation [15],... 

Netropsin Stimulates the Formation of an Extracellular Proteinase and Suppresses Protein Turnover in Sporulating Bacillus Megaterium, FEMS Microbiol. Letters, 34 21 (1986). 

We found that netropsln suppressed protein turnover but stimulated the synthesis of an extracellular metalloproteinase In Bacillus megaterlum [4]. The antibiotic affected In a similar way the formation of the proteinase not only during sporulatlon but also during growth. The effect of the antibiotic on the proteinase regulation was further studied and the results are presented In this communication. 

A purification and some properties of proteinase A from yeast are described. A specific macromolecular inhibitor of proteinase A from yeast cytosol has been isolated and shown to be a protein (molecular weight 7,700) consisting of a majority of polar amino acids. Proline, arginine, cysteine and tryptophan were not detected in the inhibitor. Possible biological functions of proteinase A and the proteinase A-inhibitor (and of other yeast proteinases and their inhibitors) in the following processes are discussed general protein turnover, catabolite inactivation of enzymes, enzyme degradation at starvation and at transition to spore formation, and activation of pre-enzymes and precursor proteins by limited proteolysis. 

Selective cleavage of peptides and proteins is an important procedure in biochemistry and molecular biology. The half-life for the uncatalyzed hydrolysis of amide bonds is 350 500 years at room temperature and pH 4 8. Clearly, efficient methods of cleavage are needed. Despite their great catalytic power and selectivity to sequence, proteinases have some disadvantages. Peptides 420,423,424,426 an(j proteins428 429 can be hydrolytically cleaved near histidine and methionine residues with several palladium(II) aqua complexes, often with catalytic turnover. 

Double-labeled proteins from rat liver cytosol ( C in long-lived, in short-liv J proteins after in vivo labeling) have been used as substrates for proteinases in vitro. The differences in the degradation rates of short-lived and long-lived proteins in vitro by different proteinases in the presence or absence of different effectors enabled conclusions to be drawn concerning their role in in vivo turnover. The main activity of lysosomal proteinases at pH values of 6.1 and 6.9 was found to be caused by thiol proteinases which decompose short-liv l cytosol proteins preferentially. Autolysis of double-labeled cell fractions showed a remarkably faster breakdown of short-lived substrate proteins only in the soluble part of lysosomes >. 

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