Enzymes.txt

• Cholesterol Synthesis
• Function: Catalyzes the creation of HMG CoA from acetyl CoA and NADPH
• First step in cholesterol synthesis

• Cholesterol Synthesis
• *Rate limiting step in cholesterol synthesis.
• Function: Catalyzes the reducing reaction of HMG CoA to mevalonic acid
• Regulated:
• 1. SREBP, which is released from the ER when cholesterol levels are low
• 2. High cholesterol decreases it (by ruining stability of mRNA)
• 3. Hormonally, insulin activates it by dephosphorylating it, glucagon deactivates by phosphorylating

• Bile acid synthesis from cholesterol
• Rate limiting step in bile acid synthesis
• Function: converts cholesterol to an intermediate that is then converted to primary bile acids (cholic acid or chenodeoxycholic acid)

• Lipoprotein Metabolism
• Function: degrades tryacylglycerols in adipose tissue
• Activated by: Apo C-II, insulin (fed state)

Function: catabolyses IDL back into LDL

• Function: esterifies cholesterol to cholesterol ester for storage
• Activated by: increased intracellular cholesterol

• Function: Esterifies cholesterol to cholesterol esters in HDL
• Activated by: Apo A-I of HDL

• Reduction of hydrogen peroxide
• Funcion: catalyzes the degredation of H₂O₂ (hydrogen peroxide) with reduced glutathione (G-SH) to H₂O and oxidized glutathione (GS-SG)

• Reduction of hydrogen peroxide
• catalyzes reaction of oxidized glutathione to reduced glutathione (G-SH), NADPH donates electrons

Function? catalyzes creation of NADPH

Function: catalyzes reaction that destroys oxygen free radicals

• Methoglobin to hemoglobin
• Function: converts oxidized cytochrome b5 back to its reduced form (using NADH as and electron donor)

• Methemoglobin to hemoglobin
• Function: catalyzes the reaction of reducing methemoglobin back to hemoglobin (cytochrome b5 is an electron donor)

• Ethanol oxidation
• Function: catalyzes oxidation of ethanol to acetaldehyde (transfers electrons to NAD⁺ to make NADH in cytosol)

• Ethanol oxidation
• Function: oxidizes acetaldehyde (from ethanol) into acetate (donates an electron to NAD⁺ to form NADH in the cytosol)

• Ethanol oxidation
• Function: oxidizes ethanol to acetaldehyde and NADPH to NADP⁺
• Induced by: chronic ingestion of ethanol

• Amino acid catabolism
• Function: funnels nitrogen from amino acids into glutamate (alpha-amino acid to alpha-keto acid--> enters TCA cycle)
• Found in: liver, kidney, intestine, muscle

• Amino acid catabolism
• Function: removes the amino group from glutamate to form free ammonia (oxidative deamination), NADH, and alpha-ketoglutarate

• Amino acid catabolism
• Function: catalyzes the transfer of the amino group from alanine to alpha-ketoglutarate to form pyruvate and glutamate (forms most of the pyruvate used for gluconeogenesis)

• Amino acid catabolism (urea cycle)
• Function: during amino acid catabolism glutamate is used to make apartate from oxaloacetate (OAA) to run the urea cycle (AST is an exception to the rule)

• Urea synthesis
• Function: rate limiting step in urea synthesis, catalyzes formation of carbamoyl phosphate from ammonia, takes 2 ATP and CO₂
• Activator: High ammonia production, N-acetylglutamate, high protein diet
• Inhibitor: Protons, low protein diet

• Urea synthesis
• Function: hydrolyzes arginine to form urea and regenerate ornithine

• Pyrimidine synthesis
• Function: catalyzes reaction that synthesizes pyrimidine in cytosol

• Function: catalyzes the sythesis of N-acetylglutamate (which activates CPSI)
• Activated by: increased concentration of acetyl CoA, and arginine

Function: converts left over ammonia into glutamine (lower Km for ammonia than CPSI, located downstream of the urea cycle in the liver to catch left over ammonia)

leucine, isoleucine and valine

• when gluconeogenesis decreases so does the urea cycle,
• when gluconeogenesis increases so does the urea cycle

• BCAA catabolism
• Function: generates BC alpha-keto acids and funnels the nitrogen into glutamate
• Where: muscle and brain
• Activated: high protein diet (for nonessential amino acids)

• BCAA catabolism
• Function: Rate limiting step in BCAA catabolism, catalyzes oxidative decarboxylation of all three branch chain alpha-keto acid dehydrogenase complexes (requires thiamine, riboflavin, niacin, pantothenic acid, and lipoic acid)
• Activated: dephosphorylation, increase in BCAAs, high protein diet
• Inhibited: phosphorylated, decrease in BCAAs, low protein diet

• Leucine (ketogenic): acetoacetate and acetyl CoA
• Valine (glucogenic): succinyl CoA
• Isoleucine (glucogenic and ketogenic): acetyl CoA and succinyl CoA

• Catecholamine sythesis
• Function: catalyzes hydroxylation of tyrosine to DOPA, rate limiting step for catecholamine synthesis (also first step)
• Requires: tetrahydrobiopterin for an electron
• Activated by: calcium/calmodulin dependent protein kinase (phophorylates it), nerve stimulation, persistant neuronal activity

• Catecholamine Synthesis
• Function: catalyzes the decarboxylation of DOPA to form dopameine
• Requires: vitamin B6

• Catecholamine synthesis
• Function: catalyzes the hydroxylation of dopamine to norepinephrine
• Requires: vitamin C and O₂
• Activated by: cortisol, presistant neuronal activity

• Catecholamine synthesis
• Function: catalyzes the cytosolic N-methylation of norepinephrine to form epinephrine
• Requires: S-adenosylmethionine (SAMe) as a methyl donor
• Enhanced by: cortisol

They are monoamine reuptake proteins that return most of the released monoamines (dopamin, norepinephrine, seretonin) to the presynaptic side

Moves catecholamines, especially dopamine into vesicles

• Catecholamine degredation
• Function: deaminates (inactivates) catecholamines (in outer membrane of mitochondria in intestine and liver)

• Catecholamine degredation
• Function: adds a methyl group to catecholamines to inactivate them (in liver and kidney)

• 9-membered bicyclic planar, aromatic rings
• DNA and RNA: Adenine (A), Guanine (G)

• 6-membered planar, aromatic rings
• DNA and RNA: Cytosine (C)
• DNA only: Thymine (T)
• RNA only: Uracil (U)

A nitrogenous base and a sugar

A phosphorylated nucleoside

• 1. Building blocks for nucleic acids
• 2. Activated intermediates for glycogen
• 3. Second messengers in signal transduction
• 4. Structural components of cofactors
• 5. Enzymes that process RNA
• 6. Energy currency within the cells

• Purine nucleotide synthesis
• Function: Rate limiting step in purine and pyrimidine nucleotide biosynthesis, catalyzes the transfer of a phosphate group from ATP to ribose-5-P to form PRPP (activated sugar)
• Activated by: inorganic phosphate
• Inhibited by: purine and pyrimidine nucleotides

• Purine nucleotide sythesis
• Function: first commuted step, replaces the phosphate group of PRPP with the amide nitrogen of glutamine
• Activator: PRPP (substrate)
• Inhibitor: purine nucleotides (AMP, GMP, IMP)

• Purine nucleotide synthesis
• 1. requires a significant amount of ATP
• 2. Needs a folate (folic acid deficiency causes anemia)
• 3. It is the first recognizable purine after all the steps
• 4. There are many steps catalyzed by multifunctional enzymes (copy machine)

• Inhibitor: AMP
• Activator: GTP

• Inhibitors: GMP
• Activators: ATP

Converts AMP to ADP

Converts GMP to GDP

Converts ADP to ATP

• Salvaging of purine nucleotides
• Function: responsible for most recycling (salvaging) of purines, converts PRPP back into GMP

• Purine degredation
• Function: removes amino group from AMP to form IMP, or removes amino group from adenosine to form inosine

• Purine degradation
• Function: catalyzes the last two steps in purine degradation, oxidation of hypoxanthine and xanthine to uric acid

Abnormally high plasma (or serum) monosodium urate concentration

100%, gout is caused by many years of hyperuricemia, not all patients with hyperuricemia have gout though

monosodium urate crystal formations

• 1. concentration of ions of urate and sodium
• 2. temperature
• 3. pH

Overproduction of uric acid (urate), 24-hour urine analysis will show uric acid production greate than normal

• 1. decrease in HGPRT activity
• 2. Overactive PRPP synthetase
• 3. Increased rate of purine degredation
• 4. Increased cell death

• Drug: Allopurinol
• Enzyme: Xanthine oxidase (it is a substrate for xanthine oxidase and after being converted to alloxanthine it inhibits xanthine oxidase as well)

Underexcretion of urate

Serine (glycine and histidine also donors of one-carbon units for one carbon metabolism)

• 1. pteridine ring
• 2. p-aminobenzoic acid (PABA)
• 3. one glutamic acid residue

A defect in the rate-limiting enzyme cystathione synthase, which is a defect in the transsulfuration pathway. (causes problems in eye, CNS, skeletal, and vascular system)

The creation of cysteine from homocysteine

• ghrelin (stomach)
• neuropeptide y (brain)

• GLP-1
• cholecystokinin (intestine)
• leptin (adipose)

It increases the rate of glycolysis, glucose uptake, phosphorylation, and catabolism (caused by an decrease in ATP and and increase in ADP which stimulates PFK-1)

Type I glycogen storage disease (G6Pase deficiency), defect in G6Pase because inability to dephosphorylate it which impairs glucose release from the liver, patients have hypoglycemia between meals