Nitrogen-Metabolism.ppt

Copyright,2013 Pearson Canada Inc.,1-,*,Click to edit Master title style,Click to edit Master title style,Copyright,2013 Pearson Canada Inc.,1-,*,Nitrogen Metabolism,Copyright,2013 Pearson Canada Inc.,20-,1,Copyright,2013 Pearson Canada Inc.,20-,2,20-,3,Sources of Nitrogen,Atmospheric N,2,NO,3,-,from lightning and rainfall,Haber Process(same Haber as in chemical warfare),Copyright,2013 Pearson Canada Inc.,1-,4,High temperature,high pressure,catalyst,Nitrogenase,Dinitrogenase component(MoFe)reduces N,2,Dinitrogenase reductase component(Fe)rereduces dinitrogenase,1-,6,N,2,+8H,+,+8 e,-,+16ATP,2NH,3,+H,2,+16 ADP,(Requires a,lot,of energy.),Copyright,2013 Pearson Canada Inc.,20-,7,So how do we use the ammonia?,:Production of Glutamate,Glutamate dehydrogenase,Reductive amination,Usually running backwards in critters due to low NH,3,Copyright,2013 Pearson Canada Inc.,1-,8,Regulation,Copyright,2013 Pearson Canada Inc.,1-,10,Glutamine is involved in the metabolism of:,Aromatic a.a.s,Several other a.a.s,Purines,Pyrimidines,Amino sugars,Regulated by feedback inhibition,Also regulated globally by signal cascades,Adenylation of tyrosine blocks active site,Asparagine synthetase,Copyright,2013 Pearson Canada Inc.,1-,11,Amino acid metabolism,Copyright,2013 Pearson Canada Inc.,1-,13,Different organisms can make different sets of amino acids.,Those we cant manufacture are essential amino acids in our diet.,Lists of essential and non-essential vary.,Amino acid synthesis:Pyruvate derivatives,Copyright,2013 Pearson Canada Inc.,1-,15,Amino acid synthesis:Ribose derivatives,Copyright,2013 Pearson Canada Inc.,1-,16,Amino acid synthesis:,a,-ketoglutarate derivatives,Copyright,2013 Pearson Canada Inc.,1-,18,Amino acid synthesis:3-phosphoglycerate derivatives,Copyright,2013 Pearson Canada Inc.,1-,19,Amino acid synthesis via transamination,Youve seen this before.,a,-Amino groups of amino acids come by transamination from Glu,You can synthesize all amino acids from their,a,-keto conjugates.,For the essential amino acids,we cant produce the,a,-keto acids.,Copyright,2013 Pearson Canada Inc.,1-,20,Also play a role in amino acid degradation,Above example is part of the degradation path for alanine.,Transamination(transfer of the amide NH,2,to,a,-ketoglutarate)yields pyruvate.,Pyruvate can be tossed into PDH and the Krebs cycle.,Copyright,2013 Pearson Canada Inc.,1-,21,Amino acid oxidases,The,a,-amino group is usually removed by transfer to,a,-ketoglutarate to yield glutamate and the,a,-keto acid.,Glutamate is then deaminated by glutamate dehydrogenase.,There are also amino acid oxidases,using a flavin electron acceptor.,Copyright,2013 Pearson Canada Inc.,1-,22,Removal of nitrogenous waste,Copyright,2013 Pearson Canada Inc.,1-,24,Insects,birds,and reptiles primarily excrete,uric acid,.,Desert mammals like kangaroo rats primarily excrete uric acid.,Oddly,so do dalmatians.,Uric acid is pretty insoluble.,In humans,it is the end product of purine catabolism.,Overproduction or underexcretion can lead to the formation of uric acid crystals frequently starting in the gravitationally lowest joints i.e.the big toe.,That condition is gout,which is often extremely painful.,Gout a surgical example in the left hand,Copyright,2013 Pearson Canada Inc.,1-,25,Removal of nitrogenous waste the urea cycle,1-,26,The universal product of degrading amino acids is ammonia.,Ammonia is toxic at not very high concentrations.,You have to get rid of it.,If you are an aquatic organism,you can just diffuse in into the environment.,We convert ammonia to urea.,The basic idea:,Add the nitrogens to ornithine to(eventually)make arginine.,Cleave the guanidino group off arginine to leave you with ornithine and urea.,Urinate out the urea.,Throw the ornithine back into the cycle.,20-,28,Ammonia transport to the liver,Urea formation takes place in the liver,Waste nitrogen is transported through the blood as Gln or Ala.,Reconverted to ammonia in the liver,