Molecules of life – dehydrogenase
August 30, 2007 on 12:08 pm | In EducationalLife is a matter of energy consumption and adoption by living organism. Each organism can only be alive when it consumes some energy. If organism does not use any energy it means that this organism is dead or is in deep-deep-deep sleep. Like some viruses or bacterial cells which can make spores and survive for thousand or even million years in almost any conditions.
Different living organisms can consume and utilize different type of energy. Most common energy is coming from the energy of chemical bonds. Other organism can consume energy from light. Some strange fungi can utilize energy of radiation.
The mechanism of chemical energy transformation and storage is involved the electron and proton transport as a main part. The electron and proton transport is performed by special proteins called dehydrogenases or oxidoreductases and oxidases. These enzymes are very different between each other.
The only common part for them – almost all of them use the same cofactor Nicotinamide adenine dinucleotide, NAD or Nicotinamide adenine dinucleotide phosphate, NADP. These cofactors are involved into central system of metabolic pathways in the living cell. NAD is the main cofactor for most dehydrogenases, the main pathway for NADH oxidation is the electron transport and oxidative phosphorilation. NADPH is usually involved as a cofactor for reductases, enzymes that catalyse substrate reduction. The main pathway for NADP reduction is the Pentose phosphate pathway. NADPH synthesized from NADH via mitochondrial energy-linked transhydrogenase. NADP synthesized from NAD by NAD -kinase with subsequent energy transduction from ATP.