Abstract
When leupeptin, a thiol protease inhibitor of microbial origin, was injected into rats, the activity of fructose-1,6-bisphosphate aldolase ( d-fructose-1,6-bisphosphate d-glyceraldehyde-3-phosphate-lyase, EC 4.1.2.13) in the liver decreased to about 60% of that in control rats. However, the concentration of aldolase protein in the liver extracts, measured with a specific antibody obtained with enzyme purified on a phosphocellulose column, remained unchanged. Injection of leupeptin also caused a marked increase in the activities of free lysosomal proteases, such as cathepsin B (EC 3.4.22.1), cathepsin L (EC 3.4.22.-), cathepsin D (EC 3.4.23.5) and lysosomal carboxypeptidase A in the cytosol fraction. A clear inverse relationship between aldolase and cathepsin B activities in the cytosol fraction was demonstrated. The possibility that the less active form of aldolase detected in the livers of leupeptin-treated rats was produced during homogenization was excluded by showing that the aldolase activity was not changed by addition of various protease inhibitors to the homogenization medium. When insulin was coinjected with leupeptin, increase in the activity of free cathepsin L and decrease of activity of aldolase produced by the injection of leupeptin was prevented. These findings indicate that modification of aldolase may be due to the action of a lysosomal protease(s). Enhanced sensitivity of lysosomes to osmotic shock was demonstrated in the livers of leupeptin-treated rats, suggesting that the lysosomal membrane is labilized by administration of leupeptin. Incubation of the purified aldolase with the lysosomal fraction produced the same changes in properties of aldolase as those observed in vivo on injection of leupeptin.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.