Zinc Enzymes

The three-dimensional structures of more than 200 zinc-containing enzymes have now been characterized, and many more enzymes have been identified. All six International Union of Biochemistry classes are represented. Zinc enzymes can be divided into three groups according to the role played by zinc within the protein. In the catalytic group (e.g., carbonic anhydrase), zinc is a direct participant in the catalytic function of the enzyme. The zinc atom is coordinated by three amino-acids from the enzyme and a molecule of water at the active site. In enzymes with structural zinc sites (e.g., protein kinase C), the metal binds four amino-acids within the protein and ensures appropriate folding for bioactivity. Enzymes in which zinc serves a co-catalytic function (e.g., superoxide dismutase) contain two or three zinc atoms, two

nucleus, MTF-1 regulates the transcription of a set of target genes, including MT and ZnT-1. MT will bind zinc, and ZnT-1 will transport zinc out across the plasma membrane. MT may govern the delivery of zinc to other proteins within the cell. Other members of the CDF family transport zinc into vesicles.

nucleus, MTF-1 regulates the transcription of a set of target genes, including MT and ZnT-1. MT will bind zinc, and ZnT-1 will transport zinc out across the plasma membrane. MT may govern the delivery of zinc to other proteins within the cell. Other members of the CDF family transport zinc into vesicles.

Table 2 Examples of mammalian zinc-dependent enzymes

Enzyme

Function

RNA polymerase

Transcription and synthesis of mRNA

Carboxypeptidase A

Protein digestion in the intestine

Protein kinase C

Signal transduction

Carbonic anhydrase

Respiration, buffering, and hydration

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