This chapter explores more metalloenzymes, considering the enzymatic activity of zinc, cobalt, and molybdenum. Zinc is the second most abundant trace element in humans and is required as an integral component of over 100 enzymes in different species of all phyla. It can play an active catalytic role, generally as a strong Lewis acid, or it can act in regulatory or structural roles. The chapter then looks at trinuclear zinc constellations, vitamin B12, nitrogenases, and oxotransfer molybdoenzymes. Molybdenum is the only element from the second and third row transition metals that has been found to be essential to life. As well as functioning in nitrogenase, it has been found to be active in oxotransfer enzymes which catalyze the transfer of oxygen atoms to, or from, a substrate and are involved in carbon, nitrogen, and sulfur metabolism. The chapter also examines nickel enzymes.
Chapter
More metalloenzymes
Chapter
The biochemistry of zinc
This chapter takes a closer look at zinc, the most abundant transition metal in all living organisms next to iron. It provides examples for the following five main categories of proteins in which zinc attains a structural function and/or mediates catalytic processes: Enzymatic activity in hydrolytic processes; substrate activation for oxidative detoxification; interconversion between carbon dioxide and hydrogencarbonate; transcription of the genetic information contained in deoxyribonucleic acid (DNA) for protein synthesis; and demethylation — and thus repair — of DNA damaged by methylation. The chapter addresses questions on how zinc ions mediate the breakdown of proteins in our food, making available amino acids for resorption and thus usage in the synthesis of our body's own proteins; how ethanol is converted to acetaldehyde; how metabolically released carbon dioxide is processed for transport into the lungs; and how the small proteins called thioneins contribute to controlling zinc homeostasis in the body.
