Thursday, April 28, 2011

Lactate Dehydrogenase...

Lactate dehydrogenase M4 (muscle) 1I10.png Lactate Dehydrogenase is the body's back-up for making energy. Under normal conditions, our bodies are able to provide enough energy via other pathways. However, when you're running late for biochem at 9 a.m. and have to sprint from your car, up the stairs, and down hallway, your body needs to rely heavily on glycolysis for its energy needs. During glycolysis, hydrogen gets transferred to NAD+ to make NADH which then passes hydrogen to Oxygen to form water; but, when there is not enough Oxygen present, NADH builds up... that's where Lactate Dehydrogenase comes into play. Lactate Dehydrogenase combines pyruvate with NADH to regenerate NAD+ for glycolysis and lactic acid (which gives you the burning feeling in your muscles during a hard work out). Unfortunately, this amazing process for energy can only be utilized for short periods of time as lactic acid needs to be converted back to pyruvate. After a short rest, however, our bodies are able to give it another go and lactate dehydrogenase can get back to work for another short burst of energy.
As mentioned previously, Lacate Dehydrogenase catalyzes the reaction that interconverts pyruvate and lactate. LDH exists in three different forms in the body: M form (structure most commonly found in muscle tissue), H form (structure found in cardiac muscle), and a third form that is found only in sperm. The M form specializes in converting pyruvate to lactate; the H form specializes in catalyzing the reverse reaction of converting lactate into pyruvate. Even though there are different kinetic properties that are associated with each form, the domain structure, subunit association, and active-site regions are indistinguishable between the two structures. Also, because the two forms are so similar, it is possible that they come together to form complexes (i.e. 2 M chains and 2 H chains). This ability to form complexes that are mixtures of both of the forms allows each cell to modify LDS to fit its own needs.

References:
http://www.rcsb.org/pdb/static.do?p=education_discussion/molecule_of_the_month/pdb102_1.html

http://www.ncbi.nlm.nih.gov/pubmed/11276087

http://en.wikipedia.org/wiki/Lactate_dehydrogenase