1. Experiments were made to determine whether the purified lysosomal proteinases, cathepsins B1 and D, degrade acid-soluble collagen in solution, reconstituted collagen fibrils, insoluble collagen or gelatin. 2. At acid pH values cathepsin B1 released 14C-labelled peptides from collagen fibrils reconstituted at neutral pH from soluble collagen. The purified enzyme required activation by cysteine and EDTA and was inhibited by 4-chloromercuribenzoate, by the chloromethyl ketones derived from tosyl-lysine and acetyltetra-alanine and by human α2-macroglobulin. 3. Cathepsin B1 degraded collagen in solution, the pH optimum being pH4.5–5.0. The initial action was cleavage of the non-helical region containing the cross-link; this was seen as a decrease in viscosity with no change in optical rotation. The enzyme also attacked the helical region of collagen by a mechanism different from that of mammalian neutral collagenase. No discrete intermediate products of a specific size were observed in segment-long-spacing crystalloids (measured as native collagen molecules aligned with N-termini together along the long axis) or as separate peaks on gel filtration chromatography. This suggests that once an α-chain was attacked it was rapidly degraded to low-molecular-weight peptides. 4. Cathepsin B1 degraded insoluble collagen with a pH optimum below 4; this value is lower than that found for the soluble substrate, and a possible explanation is given. 5. The lysosomal carboxyl proteinase, cathepsin D, had no action on collagen or gelatin at pH3.0. Neither cathepsin B1 nor D cleaved Pz-Pro-Leu-Gly-Pro-d-Arg. 6. Cathepsin B1 activity was shown to be essential for the degradation of collagen by lysosomal extracts. 7. Cathepsin B1 may provide an alternative route for collagen breakdown in physiological and pathological situations.
Skip Nav Destination
Article navigation
February 1974
-
Cover Image
Cover Image
- PDF Icon PDF LinkFront Matter
- PDF Icon PDF LinkTable of Contents
- PDF Icon PDF LinkAdvertising
Research Article|
February 01 1974
Cathepsin B1. A lysosomal enzyme that degrades native collagen
Mary C. Burleigh;
Mary C. Burleigh
1Tissue Physiology Department, Strangeways Research Laboratory, Cambridge CB1 4RN, U.K.
Search for other works by this author on:
Alan J. Barrett;
Alan J. Barrett
1Tissue Physiology Department, Strangeways Research Laboratory, Cambridge CB1 4RN, U.K.
Search for other works by this author on:
Gerald S. Lazarus
Gerald S. Lazarus
1Tissue Physiology Department, Strangeways Research Laboratory, Cambridge CB1 4RN, U.K.
Search for other works by this author on:
Publisher: Portland Press Ltd
Online ISSN: 1470-8728
Print ISSN: 0264-6021
© 1974 London: The Biochemical Society
1974
Biochem J (1974) 137 (2): 387–398.
Citation
Mary C. Burleigh, Alan J. Barrett, Gerald S. Lazarus; Cathepsin B1. A lysosomal enzyme that degrades native collagen. Biochem J 1 February 1974; 137 (2): 387–398. doi: https://doi.org/10.1042/bj1370387
Download citation file:
Sign in
Don't already have an account? Register
Sign in to your personal account
You could not be signed in. Please check your email address / username and password and try again.
Could not validate captcha. Please try again.