Iron protein other biochemical reactions

The role of the transition elements in living systems is equally important. Iron is present in biomolecules such as hemoglobin, which transports oxygen from our lungs to other parts of the body. Cobalt is an essential component of vitamin B12. Nickel, copper, and zinc are vital constituents of many enzymes, the large protein molecules that catalyze biochemical reactions. 

In order to carry out most biochemical reactions, metalloenzymes generally utilize the rarer transition metal ions. Elements such as zinc, copper, iron, nickel, and cobalt are found in low concentrations in plasma and seawater and yet the enzyme has to select the appropriate metal ion from them. There is evidence for the existence of proteins that can chaperone specific metal ions to their appropriate sites in apoenzymes, protecting the metal ions from adverse reactions as they are guided to their required location [5]. How does the enzyme attempt to select out the one metal ion it requires The answer is that the chemistry of the metal ion is used as a basis for selection. Each metal ion has some property that is different from that of most others, but, in fact, there is often considerable overlap in these properties so that a given enzyme may bind one of several different cations in one specific site. Some relevant data are provided in Tables 1 and 2. The metalloenzyme contains within its overall design an arrangement of preferred side-chain functional groups with the correct size hole to bind the required metal ions in an appropriate hydrophobic or hydrophilic environment. Thus the metalloenzyme binds metal ions... 

By virtue of unoccupied d-orbitals, iron binds to many ligands - preferably to their oxygen, nitrogen, and sulfur atoms. In enzymes and other metalloproteins, iron participates in a large number of biochemical reactions. Its chemical reactivity changes due to the oxidation state, electron spin state and redox potential, the latter ranging from +1000 mV in some heme proteins to —550 mV in some bacterial ferredoxins (Cammack et al. 1990). 

---