Changes in carbon sources fueling benthic secondary production over depth and time: coupling Chironomidae stable carbon isotopes to larval abundance.

Stable C isotope ratio (δ(13)C) values of chironomid remains (head capsules; HC) were used to infer changes in benthic C sources over the last 150 years for two French sub-Alpine lakes. The HCs were retrieved from a series of sediment cores from different depths. The HC δ(13)C values started to decrease with the onset of eutrophication.

The slow-binding inhibition of cathepsin K by its propeptide.

A peptide corresponding to the full-length proregion (amino acids 16-114) of human cathepsin K was expressed and purified from Escherichia coli. This recombinant propeptide was investigated for its ability to inhibit the activity of three cysteine proteinases: cathepsins K, L, and B. Kinetic studies showed the propeptide to be a potent slow-binding inhibitor of its parent enzyme with a K(i) = 2.

Cathepsin B: an alternative protease for the generation of an aggrecan 'metalloproteinase' cleavage neoepitope.

Previously, only matrix metalloproteinases were believed capable of cleaving the cartilage proteoglycan, aggrecan, between Asn341 and Phe342, to yield a small G1 fragment terminating in the residues VDIPEN. We show that the combined endo- and exopeptidase activities of the cysteine protease, cathepsin B, also generate this epitope, suggesting that it should no longer be considered as an exclusive marker of metalloproteinase activity.

Immunolocalization of the cleavage of the aggrecan core protein at the Asn341-Phe342 bond, as an indicator of the location of the metalloproteinases active in the lysis of the rat growth plate.

In view of the extensive lysis of hyaline cartilage known to take place during endochondral bone formation, the current study was designed to test the hypothesis that metalloproteinases are the agents that mediate this lysis. Since these enzymes have been shown in vitro to cleave the core protein of the major proteoglycan of cartilage, aggrecan, at the Asn341-Phe342 bond, an immunohistochemical method has been developed to find out whether or not there are sites in the growth plate of the rat tibia where cleavage of this bond takes place. The cleavage of aggrecan by metalloproteinases is followed by the retention of the fragment known as G1, for it includes the G1 domain.

An NMR-based identification of peptide fragments mimicking the interactions of the cathepsin B propeptide.

Selected fragments of the 62-residue proregion (or residues 1p-62p) of the cysteine protease cathepsin B were synthesized and their interactions with cathepsin B studied by use of proton NMR spectroscopy. Peptide fragments 16p-51p and 26p-51p exhibited differential perturbations of their proton resonances in the presence of cathepsin B. These resonance perturbations were lost for the further truncated 36p-51p fragment, but remained in the 26p-43p and 28p-43p peptide fragments.