RESUMEN
The inner shell coordination properties of zinc proteins have led to the identification of four types of zinc binding sites: catalytic, cocatalytic, structural, and protein interface. Outer shell coordination can influence the stability of the zinc site and its function as exemplified herein by the zinc sites in carbonic anhydrase, promatrix metalloproteases and alcohol dehydrogenase. Agents that disrupt these interactions, can lead to increased off rate constants for zinc. D: -penicillamine is the first drug to inhibit a zinc protease by catalyzing the removal of the metal. Since it can accept the released zinc we have referred to it as a catalytic chelator. Agents that catalyze the release of the metal in the presence of a scavenger chelator will also inhibit enzyme catalysis and are referred to as enhanced dechelation inhibitors.
Asunto(s)
Metaloproteínas , Zinc , Alcohol Deshidrogenasa/química , Alcohol Deshidrogenasa/genética , Alcohol Deshidrogenasa/metabolismo , Secuencia de Aminoácidos , Sitios de Unión , Anhidrasas Carbónicas/química , Anhidrasas Carbónicas/genética , Anhidrasas Carbónicas/metabolismo , Catálisis , Humanos , Metaloproteínas/química , Metaloproteínas/metabolismo , Modelos Moleculares , Datos de Secuencia Molecular , Conformación Proteica , Precursores de Proteínas/química , Precursores de Proteínas/genética , Precursores de Proteínas/metabolismo , Alineación de Secuencia , Zinc/química , Zinc/metabolismoRESUMEN
The antiarthritis drug D-penicillamine (D-PEN) catalyzes zinc(II) transfer from carboxypeptidase A to chelators such as thionein and EDTA at a rate constant up to 400-fold faster than the uncatalyzed release. Once D-PEN releases zinc(II) from enzyme stronger chelators can tightly bind zinc(II) leading to complete and essentially irreversible inhibition. D-PEN is the first drug to inhibit a zinc protease by catalyzing metal removal, and the name "catalytic chelation" is proposed for this mechanism.
Asunto(s)
Carboxipeptidasas A/antagonistas & inhibidores , Quelantes/química , Ácido Edético/química , Ergotioneína/química , Penicilamina/química , Zinc/química , Animales , Carboxipeptidasas A/química , Catálisis , Bovinos , Sinergismo Farmacológico , CinéticaRESUMEN
A low-temperature rapid-mixing and flow system has been designed and implemented to monitor catalysis involving metal ions by X-ray absorption spectroscopy at the ID-18 beamline of the Advanced Photon Source, Argonne National Laboratory. The system will allow examination of biological metallo-intermediates at dilute metal ion concentrations by the detection of X-ray fluorescence. The instrument can be cooled to sub-zero temperatures, thus lengthening the life time of a reaction intermediate. A portable UV-visible spectrometer is integrated with the flow system to monitor the sample optically. The system can also be used as a continuous-flow device to minimize radiation-induced sample damage by reducing sample exposure to the X-ray beam. The integration of the stop-flow instrument with the synchrotron beamline and X-ray fluorescence detector systems makes it unique for time-resolved X-ray absorption studies of dilute biological reactions. The results of the initial testing of the system are presented.