BIOL 541 1st Edition Lecture 14 Outline of Last Lecture I. Glycolysis in tissues Outline of Current Lecture II.Liver function and locationIII. Structure of enzymesIV. TCA cycleCurrent LectureBiochem Lecture 14- Glycolysis in liver:Glucokinase an isomer of hexokinase is present as there are no glucose 6 phosphate in liver but in peripheral tissue.Liver function and location:Blood in the heart enters into arteries and then into capillary beds and then organs. Blood leaves via veins which forms large veins that drain into heart. Another system is where the veins go into secondary organs forming secondary capillary bed and then draining into veins and entering back into the heart. There are 2 capillary bed systems: one is hepatic portal system. The abdominal aorta enters the intestines and then becomes hepatic portal veins which further divide into capillaries in the liver. The liver is the hub of metabolic activity where liver absorbs glucose and converts it to glycogen for storage. Further, co factors as well as iron are also stored here. There are no feedback inhibition of glucose 6 phosphate so no glucose 6 phosphate is present in the liver.GKRP (glucokinase regulatory protein) is an inhibitory protein. During low levels of energy or when back up of materials occurs, glucose uptake is shut down. During fasting, liver exports glucose and gluconeogenesis occurs instead of glycolysis. AMP is phosphorylated and GKRP is activated by fructose 6 phosphate. This is competitive inhibition and occurs in the nucleus whereas glycolysis occurs in the cytosol.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.Glucose 6 phosphate conversion to fructose 6 phosphate is at equilibrium. Phosphofructokinase has the same activator fructose 2,6 bisphosphate and is generated by a different isozyme. In peripheral tissues, phosphorylation regulates phosphatase and kinase. AMP kinase phosphorylates this and phosphatase and acts as allosteric activator and stimulate kinase. So glucose is broken during fasting.There are different splicing theory of isozyme and no axon of AMP phosphorylate this site. Protein kinaseA has a different axon. When CMP level is elevated during fasting, glucagon and epinephrine, which are hormones needed for energy mobilization, are also elevated. In the liver, glucose is present for energy. Glucagon generate cAMP and phosphorylate liver enzyme and favors phosphatase to be activated. Whenfructose 2,6 bisphosphate is acted upon by phosphofructokinase and levels of phosphofructokinase decreases glycolysis is turned off and gluconeogenesis is turned on.Cross talk between 2 irreversible and regulated steps:Glucose 6 phosphate (product of glucokinase) stimulates PFK2 and allosteric activates phosphatase. Therefore, phosphate is removed and kinase added as feed forward reaction. PFK2/FBP2 kinase activatesphosphatase. PFK2 unphosphorylated form activates FBP2. Glycolysis is activated , therefore glucokinase needs more glucose for pathways.In fat tissues: Covalent modification: NAG is added to proteins.Glucose is phosphorylated to glucose 6 phosphate where C=O is flipped to give fructose 6 phosphate.GF6P amidotransferase takes an amide from glutamine to form fructose 6 phosphate and glucosamine 6 phosphate forms. It is inhibited by PKA and AMPK phosphatase. It is acetylated by acetyl COA to form NAG.Sugar needs are activated by coupling to the nucleotide uridine triphosphate.This is a feed forward reaction where the increase in glucose level drives modification.Insulin is an anabolic hormone which has receptor TYR kinase and activates the enzyme to increase glucose level and favors glycogen synthesis. Protein synthesis and fatty acid synthesis need lots of H andH comes from NADPH from PPP. Insulin receptor TYR phosphorylated and activates phosphatase. NAG is attached to phosphofructokinase and blocks glycolysis. Therefore, glucose goes to PPP and generates H to make fatty acids.Fatty acids are made for storage when excess carbohydrates are present. If deficiency during fasting is seen, this process is turned off. Increasing levels of AMP, increasing levels of glucagon, thereby increasing levels of PKA block amidotransferase and AMP blocks transferase. In other words, lots of glucose, this reaction occurs, and if less glucose is present then the reaction is inhibited. Also, anabolic levels increase, this reaction is favored and catabolic reactions inhibit this reaction.Last step:Pyruvate kinase is regulated in tissues. In liver, in case of pyruvate kinase phosphorylation of protein kinase A inhibits the enzyme. During starvation, glucagon level increases, protein kinase A phosphorylates and inactivates pyruvate kinase.Gluconeogenesis occurs in liver during fasting. Phospho enol pyruvate carboxylates pyruvate to oxaloacetate using pyruvate kinase.Oxaloacetate by PEP carboxy kinase is converted to PEP to make more glucose. PEP caboxykinase is inhibited by acetylation.During fasting, increasing levels of NAD is co substrate for deacetylation and removes inhibition. Therefore, PEP carboxy kinase is activated and gluconeogenesis is stimulated.1 molecule of glucose gives 2 molecules of pyruvates. TCA is going to accept acetyl COA which is broken down into CO2 and water. In other words, pyruvate is converted to acetyl COA in TCA.This reaction is catalysed by 3 enzymes called pyruvate dehydrogenase:1. Pyruvate dehydogenase uses TPP as co enzyme and attaches to alpha C and CO2 is released. Attached to TPP and transfer to dihydolipoyl transacetyl lipoamide (disulphide bond at the end) and transfer to COA and feed it into TCA. 2. Reduced lipoic acid is oxidized by dilipoyl dehydrogenase and disulphide bonds are regenerated by H. H goes to NAD.Structure of enzyme (metabolon): It is present in a multi subunit complex. In prokaryotes, 60 subunits-E1 24E2 24E3 12Total 60In eukaryotes,E1 30 X 4E2 60E3 12E3 12 Extra binding protein for maintaining structure. Enzyme is regulated by phosphorylation of kinase and phosphatase is also part of it. Pyruvate dehydrogenase is a tetramer with over 200 proteins. All are coded by nuclear genes. Glycolysis occurs in cytoplasm. Pyruvate enters the mitochondria where pyruvate dehydrogenase is located as well as some pyruvate dehydrogenase occurs in nucleus. Acetylation in enzyme activity and