Naslov
Reactivity and functional significance of cysteine residues of mammalian dipeptidyl peptidases III

Autori
Abramić, Marija ; Šimaga, Šumski ; Osmak, Maja ; Čičin-Šain, Lipa ; Vukelić, Bojana ; Vlahoviček, Kristijan ; Dolovčak, Ljerka

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
The FEBS Journal, Vol. 272 Suppl. 1, July 2005 / Perham, Richard - Oxford : Wiley-Blackwell, 2005, 414 - 415

Skup
30th FEBS Congress and 9th IUBMB Conference, THE PROTEIN WORLD

Mjesto i datum
Budimpešta, Mađarska, 02.07.2005. - 07.07.2005

Vrsta sudjelovanja
Poster

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
Dipeptidyl peptidase III; Reactive SH-groups; Oxidant; Redox regulation; Rat tissues

Sažetak
Dipeptidyl peptidase III (DPP III) is a cytosolic zinc-exopeptidase involved in the intracellular protein catabolism of eukaryotes. Although inhibition by thiol reagents is a general feature of DPP III originating from various species, the function of activity important sulfhydryl groups is still inadequately understood. The present study of the reactivity of these groups was undertaken in order to clarify their biological significance. The inactivation kinetics of human and rat DPP III by sulfhydryl reagent p-hydroxy-mercuribenzoate (pHMB) was monitored by determination of the enzyme’ s residual activity with fluorimetric detection. Inactivation of this human enzyme exhibited pseudo-first-order kinetics, suggesting that all reactive SH-groups have equivalent reactivity, and the second-order rate constant was calculated to be 3520 M-1min-1. Rat DPP III was hyperreactive to pHMB and showed biphasic kinetics indicating two classes of reactive SH-groups. The second-order rate constants of 3540 M-1s-1 for slower reacting sulfhydryl, and 21, 855 M-1s-1, for faster reacting sulfhydryl were obtained from slopes of linear plots of pseudo-first-order constants versus reagent concentration. Peptide substrates protected both mammalian DPPs III from inactivation by pHMB. Physiological concentrations of biological thiols and H2O2 inactivated the rat DPP III. Human enzyme was resistant to H2O2 attack and less affected by reduced glutathione than the rat homologue. A significantly lower DPP III level, determined by activity measurement and Western blotting, was found in the cytosols of highly oxygenated rat tissues. These results provide kinetic evidence that cysteine residues are involved in substrate binding of mammalian DPPs III.

Izvorni jezik
Engleski

Znanstvena područja
Kemija, Biologija

POVEZANOST RADA