The ins and outs of biological zinc sites.

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.

Catalysis of zinc transfer by D-penicillamine to secondary chelators.

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.

A versatile rapid-mixing and flow device for X-ray absorption spectroscopy.

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.