English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

The thyroglobulin type-1 (Tg-1) domain is a protein module that occurs in a variety of secreted and membrane proteins and is recognised as a potent inhibitor of cysteine peptidases. We present here some properties of the Tg-1 domain of human testican, a modularly organised proteoglycan secreted mainly by brain cells, the exact  in vivo  function of which is not yet clear. The domain was prepared as a recombinant protein in a  Pichia pastoris  expression system and its activity was demonstrated by specific and selective inhibition of cathepsin L ( K  i =0.14 nM). Interaction at high enzyme and inhibitor concentrations resulted in degradation of the domain by cathepsin L, which was not observed under conditions used for the determination of kinetic parameters. No inhibitory activity could be detected for cathepsin K, but it exhibited a very similar degradation pattern. Homology modelling provided a good explanation for the different behaviour observed with the two enzymes. Firstly, the steric fit between the interfaces of testican domain and cathepsin L is stabilised by numerous favourable forces, while no such interactions are evident in the complex with cathepsin K, and repulsive interactions even prevent access of the domain to the active site of papain. Secondly, the prolonged first loop of the domain occupies a position near the catalytic cysteine residue in a more substrate-like manner, enabling cleavage of the Gly 22 -Ala 23  bond.

Dual concentration-dependent activity of thyroglobulin type-1 domain of testican: specific inhibitor and substrate of cathepsin L