Identification of the thyrotropin-releasing-hormone-degrading ectoenzyme as a metallopeptidase.

ABSTRACT: A time-dependent inhibition of the thyrotropin-releasing-hormone (TRH)-degrading ectoenzyme (EC 3.4.19.-) from rat brain by the metal-complexing agents imidazole, NaCN, EDTA and 1,10-phenanthroline could be demonstrated. In contrast, the inhibition by the non-chelating analogues 4,7- and 1,7-phenanthroline was not time-dependent. At a concentration of 100 microM EDTA the enzymic activity decreased by 50% only after pretreatment for 6 h. It could be restored by addition of Zn2+, Ni2+ and Co2+ but not by other transition metal ions and also not by Ca2+ and Mg2+. Without pretreatment, the enzyme was activated by Co2+ and inhibited by Cu2+, Cd2+ and Hg2+ in a time-dependent manner, but remained unaffected by Ni2+ and Mn2+, as well as by Ca2+ and Mg2+. Compatible with the His-Glu-Xaa-Xaa-His co

SUBMITTER: Czekay G 

PROVIDER: S-EPMC1132368 | biostudies-literature | 1993 Mar

REPOSITORIES: biostudies-literature