Question

Choose one of the three general functional classes of zinc (catalytic, structural, regulatory) and discuss the biochemical and physiologic functions. Provide an example from the functional class you chose.

Answer 1

Zinc has been an important constitutent in human body to carryout the physiological functions in a ballanced way within a defined cellular component. The activities of zinc in the biochemicla and physiological process has been classified under 3 heads- catalytic, structural and regulatory.

1- Catalytic- By catalytic activity we mean to increase the efficiency or rate of a function by attaching with the species.

-Biochemical Role-   Zinc is required for the activity of more than 300 enzymes, covering all six classes of enzymes. It can activate the substrates in enzymes by stabilizing negative charges present their due to its property of Lewis Acid (i.e it can accept the electron, thus stabilises the -ve charge at the substrate.

  Within proteins, zinc can be coordinated by nitrogen, oxygen, and sulfur atoms. Thus either participate directly in chemical catalysis or maintain the protein structure and stability.

Physiological Role- Zinc accumulation in subcellular compartments is found in specific processes.

For example, large amounts of zinc are localized at the cortical granules of oocytes (in females) during meiotic maturation from the prophase I to the metaphase , which is required for growth arrest after the first meiotic division . The accumulated zinc is ejected from the oocyte to decrease bioavailable zinc during egg activation immediately following intracellular calcium oscillations, which is termed the “zinc spark” .

It also plays crucial role in signaling where it acts as a second messenger to signal the cells regarding its functions. This signaling is caused by Zinc influx. The signaling functions of zinc occur by increases in zinc concentrations triggered by stimuli. Zinc-activated signaling is associated with pathophysiological functions and therefore has therapeutic potential.

Extracellular release of zinc acts as a signaling mediator in endocrine, paracrine, and autocrine systems. In the central nervous system, zinc, which is released from presynaptic neurons, modulates synaptic transmission by binding to various transporters and receptor channels on postsynaptic neurons.