BIOL 541 1st Edition Lecture 20 Outline of Last Lecture I. Fatty acid synthesis. Outline of Current Lecture II.Detoxify NIII. Energy calculationsIV. Regulation and side products.Current LectureBiochem lecture 20- Detoxifying nitrogen:This takes place in liver via urea cycle, part of it takes place in mitochondria and part of it in the cytoplasm.Ammonia from glutamate dehydrogenase reaction takes place to form carbomoyl phospahate (high energy reaction requires 2 ATP).Carbomoyly phospahate is rammed into end by onithine (side chain like LYS except 1 less C in side chain).Not incorporated in protein synthesis but synthesis of poly amines for translation and transcription- binds to DNA and stabilize it- enzymatically synthesized. Attached to NH2 group forming citrulline. Last step is transaminationof C=O. N comes from amino acid breakdown (transamination reaction). Amino acid transfers NH2 group to oxaloacetate. Asparatic acid (amino acid) becomes keto acid and is broken down.2nd transamination reaction:ASP acid does not want to let go but hybrid formed- arginino succinate (arginino succinate synthetase 2 ATP-- 2AMP reaction is at equilibrium). Para phospahate is split to drive the reaction. 2 high energy phosphate bonds and 2 more ATP formed.ASP acid is ripped off. N is left behind and = bond and pulled off to form fumarate. ARG is done. Urea cycle doubles as ARG synthesis pathway. Arginase is cut and ornithine regenerated, ornithine + carbomoyl phosphate react again.Urea (beningn) 1. N from ammonia, 2. N transferres to oxaloacetate and citrulline.These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.Oxaloacetate regenerated by adding water across = bond and malate formed. Oxidize OH to ketone and oxaloacetate ready to pick up another N.Energy:NAD from malate and oxaloacetate strips ammonia from gluatamate.3 ATP/ NADH= 3x 2= 6 ATP.2ATP consumed by carbomyl phosphate and 2 ATP consumed by ligation of citrulline.6 ATP -4 ATP = 2 ATP or 1 ATP / N.Regulation of urea cycle:Rate limiting step is arginino succinate synthetase and is highly regulated. Regulation is in 3 ways depending upon location in tissues.1. Liver- urea cycle- elimination of N. Primarily done by gene induction and repression. It is stimulated by cortisol and glucagon which are elevate during fasting, thereby N is generated and activates urea cycle. Glutamine (storage of N) accumulation stimulates urea cycle. Insulin (anabolic hormone) blocks effect of cortisol induction.2. In placenta, small intestine of fetus, kidney of child and adult serve as ARG synthesis pathway.3. Other cells used to generate nitric oxide, where 1 N is oxidized to nitric oxide and regenerate citrulline (abbreviated cycle). NO released during inflammation causing vasodilation and kills micro organisms. Macrophages are induced by cytokines which stimulate the immune cells and PKA phosphorylation.Enzymes regulated by acetylation:Acetylation represents energy, therefore inhibits protein synthesis and their enzymes including carbomyl phosphate synthetase, ornithine transcarbomylase, and arginino succinate lyase. Deacetylation activates these enzymes as acetylation is stopped.Genetic disorders:Increase in ammonia levels is seen in liver diseases due to viral, hepatitis, and cirrhosis of liver.C- skeletons:3families of them are considered for energy calculations:1. Catabolism of ASP acid:Transamination gets rid of 1 N (1 ATP) and generate oxalo acetate (enters top of TCA cycle). 4C compound and 2 turns therefore 2x12= 24 ATP + 1ATP (from N) = 25 ATP.For ASP 1 more N(amide), so 26 ATP.2. Pyruvate:ALA (transamination) 1 ATPKeto acid (pyruvic acid -acetyl COA by pyruvate dehydrogenase where H goes to NAD (3 ATP)Acetyl COA to TCA cycle 12 ATPTotal= 12 + 3 + 1=16 ATP.3. CYS: First, oxidize S (removal of H), NAD acceptor, performed by CYS dioxygenase oxidize by using molecular oxygen of H recipient. Water formed by passing ETC (no energy generated).In addition, it uses 3 CYS as co-factor (regulation): Increase in level of CYS, activated to get rid of excess and inactivated when CYS levels are low.Second, strip off N- 1 ATP.S transferred to another enzyme such as zanthin oxidase.Lastly, pyruvate yielded which forms 3 acetyl COA- 15 ATP= Total= 15+1=16 ATPSER:Strip off as ammonia dehydration reaction 1N -1ATPKetone formed as pyruvate 16 ATP.GLY broken down in pairs:1 GLY ripped off by oxidative decarboxylation, as well as ammonia ripped off.OH methyl group rammed onto another GLY to form SER.Oxidation of NAD carrier + 1 N of GLY=3+1=4 ATPSER generates 16 ATP = Total= 16+4=20 ATP for 2 GLY. 10 ATP/ GLY.Important uses for side products:Folic acid is an important enzyme for C group transfer. C comes from GLY breakdown and done by GLY cleavage complex and source is limiting during growth. In addition body uses GLY as an inhibitory neurotransmitter. Mutation leads to this breakdown impairment of GLY and excessive suppression of nervous system as lethargy and apnea develop.THR:This is broken down just like fatty acids where OH is oxidized and FAD is the H acceptor instead of NAD which gives 3 ATP.Split the molecule to form acetyl COA -12 ATP. + GLY 10 ATP= Total= 12+10=25 ATPLast family: Alpha keto glutarate:Break down opposite of synthesis (not HIS).Glucose transamination forms 1 ATP.Alpha keto glutarate is fed into TCA cycle after 1st oxidation step. 5C added to TCA at top and form oxaloacetate-24 ATP.Oxalo acetate 4 C and 2 turns.Oxalo acetate to succinyl COA (NAD)-3 ATPCOA to GTP to ATP 4ATPSuccinate to pyruvate uses FAD 2 ATPWater is added to double bond, malate is converted to oxaloacetate.NAD 3 ATP=9ATP +24 ATP= 33 ATP. N 1 ATP= 33+1= 34 atp.GLN 1 more N= 34+1=35 ATPGLN as glutamine.Proline synthesis:PRO is synthesized from GLU acid where reduce COOH to aldehyde and amino groups as shift spaces. 2 separate molecules but aldehyde and amino group form intramolecular shift space. Double bond is reduced to PRO and broken.Reducing is done by oxygenase and generates no ATP.Shift space (open and close)reform aldehyde and amino group to acid and NAD also forms. Thus, 3 ATP+GLN.ARG:Split off urea to give ornithinine.Transamination gives 1 ATPRegenerate C=O (in form of aldehyde).Oxidized to GLN acid = 35+4=39 ATPWhere amino acids end up to:Amino acid fed via succinyl COA:MET transfers methyl