Enzymes And Isoenzymes Flashcards
What indicates whether the reaction will proceed without the input of energy but are not indicative of the velocity at which the reaction takes place?
Numerical values of the standard free energy change
What enzyme increases the amount of times carbon dioxide and water coverts to bicarbonate and hydrogen?
Carbonic acid
What are the most important class of biochemical reactions given that biological oxidation provides most of the energy for aerobic metabolism?
Redox reactions
When is energy released through the electron transportt chain?
When electrons are transferred from fuel molecules through the ETC to oxygen
Energy released in the ETC is used for what?
pump hydrogen ions across the mitochondrial membrane
How can kidneys regulate the pH of blood?
They have the ability to remove protons from the blood in the form of ammonium ion and to reabsorb bicarbonate
What does low pH trigger in the kidney?
An increase in both the removal of protons and the reabsorption of bicarbonate
Diabetic ketoacidosis is a condition marked by what?
hyperglycemia and low blood pH that often afflicts individuals with uncontrolled diabetes
The lack of insulin prevents glucose from being taken up by cells to produce energy and consequently, the body switches to degrading _______ for energy.
fatty acid
The degradation via beta-oxidation of fatty acids generates acidic compounds called _______.
ketone bodies
What are examples of ketone bodies?
acetone, acetoacetic acid, beta-hydroxybutyric acid
The dissociation of ketone bodies releases what?
H, which causes the pH of blood decrease
What are the symptoms diabetic ketoacidosis?
dehydration, vomiting, confusion, and coma and may lead to death
Describe the gastric proton pump
H/K ATPase pump located in parietal cells that line the gastric lumen, pumps protons into gastric lumen, where they combine the Cl to create HCl, a key component of gastic acid
What are drugs that inhibit the gastric proton pump?
omeprazole, iansoprazole, esomeprazole.
What does the reduction of HCl production cause?
Hypocholorhydria, which leads to a decrease in the absorption of nutrients, an increase in sensitivity to food poisoning, and a reduction in the efficacy of gastric enzymes
What is a pharmaceutical agent used for the treatment of chronic gout- a condition caused by the accumulation of uric acid in the synovial fluids surrounding joints and marked by throbbing pain due to the inflammation of joints?
allopurinol
What is the target of allopurinol?
Xanthine oxidase; converts hypoxanthine to xanthine and then uric acid in purine degradation
Why is allopurinol often described as suicide inhibitor/inactivator?
bc its mechanism of action involves binding to the active site of xanthine oxidase, which then converts allopurinol into its active metabolite, alloxanthine. The latter binds tightly to the active site and is only slowly released from it.
At low concentrations, allopurinol is described as a ________ inhibitor, but at high concentration, it is described as ______ inhibitor?
competitive, noncompetitive
What is an autoimmune disease caused by an inhibition of acetylcholine signaling by antibodies that bind to and thus block acetylcholine nicotinic receptors from binding to their cognate ligand, acetylcholine?
myasthenia gravis
Patient shows signs of muscle weakness, inability to hold one’s gaze, and fatigue. What is the disease and recommended treatment?
Myasthenia gravis
Acetylcholinesterase inhibitors such as physostigmine, neostigmine, and pyridostigmine (reversible inhibitor)
What inhibits metalloenzymes?
chelating agents that bind to and remove the metal cofactors from the metalloenzyme. Ethylenediaminetetraacetic acid
Patient; 8 shows symptoms: abdominal pain, sideroblastic anemia, irritability, headaches, and signs of impaired nervous development and encephalopathy. Patient lives in older building dating back to 1960. Diagnosis
Possible lead poisoning. Lead inhibits ALA dehydratase and ferroochelatase, enzymes involved in the biosynthesis ofheme. Treatment with EDTA because lead has an higher affinity for EDTA than does calcium and is excreated in the urine. Children can be treated with chelating agent succimer
What is troponin?
a protein complex that plays a role in muscle contraction and relaxation triggered by elevated or depressed levels of intracellular Ca respectively
What is TN-I?
Inhibitory subunit of troponin. cTn-I is found in cardiac muscle. Its serum levels increase after a myocardial infarction
In bone disease, higher levels of what enzyme can be expected in the serum?
Alkaline phosphatase
Obstructive liver disease will cause what enzyme concentrations to be increased in the serum?
Sorbitol dehydrogenase
Lactate dehydrogenase
If elevated levels of acid phosphatase if found in serum, what diagnosis can be determined?
Prostatic cancer
Increased levels of amylase in the serum can indicate what disease?
Acute pancreatitis
increased levels of aldolase and aspartate aminotransferase in the serum can indicate what disease?
muscular dystrophy
Increased levels of ALT and CK-MM isoform of creatine kinase in the serum can indicate what disease?
liver disorder
What causes respiratory acidosis?
Hypoventilation leads to an increase in the concentration of CO2 in blood. Reaction is shifted to the left which causes an increase in H
What causes metabolic acidosis?
Addition of a strong acid (lactate, ketone bodies)
Loss of bicarbonate via diarrhea and weakened kidney function
What causes respiratory alkalosis?
Hyperventilation leads to a decrease in the concentration of CO2 in the blood As a result, the reaction shifts to the right which H decreases
What causes metabolic alkalosis?
Addition of a strong base like antacid
Loss of acid via vomiting
What class of enzymes transfer electrons from a donor to an acceptor? Give an example
Oxidoreductases
Dehydrogenases
What class of enzymes transfer a functional group between molecules? Give an example
transferases
Phosphotransferases
What class of enzymes rearrange molecules? Give an example
isomerases
Epimerases
Triose phosphate isomerase
What class of enzymes add or remove atoms to or from a double bond? Give an example
Lyases
C-N-lyases
What class of enzymes form bonds with the hydrolysis of ATP?
Ligases
What class of enzymes cleave bonds via the addition of water? Give an example
hydrolases
Esterases, glycosidases, peptidases
In peptide hydrolysis, what acts as a general base catalyst and why?
The His-57
In the presence of the substrate, His-57 accepts the proton from the Ser-195 hydroxyl group
What are small molecules that contribute to the chemical reaction of the enzyme?
cofactors
Enzyme without its cofactor is called ______.
apoenzyme
Enzyme bound to cofactor and catalytically active is called _______.
haloenzyme
Describe metal cofactors
Positively charged
Stable coordination of active site groups
Contribute to chemical reactivity
What enzyme requires Cu for activity and is part of the ETC?
Cytochrome c oxidase
What enzyme requires Cu and synthesizes melanin?
tyrosinase
Fe is a metal ion required for activity of what protein?
Heme proteins
Name two important enzymes that require Mg for activity
ATPase
Adenylate cyclase
Kinases
What enzyme detoxifies hydrogen peroxide and uses cofactor Se?
glutathione peroxidase
Alcohol dehydrogenase, carbonic anhydrase and transcription factors use what cofactor?
Zn
Small organic molecules often derived from vitamins are called ______ and when bound tightly are called _______.
Coenzymes
Prosthetic group
Patient symptoms: lesions in corner of mouth and on lips, UV sensitive
Ariboflavinosis, coenzyme riboflavin B2 is deficient.
Required for FAD synthesis
Low FAD reduces glutathione reductase activity: cleans up ROS
What happens in the active site of alcohol dehydrogenase?
NAD+ is reduced to NADH in the conversion of ethanol to acetaladehyde
Cofactors: NAD+ and Zn
What catalyzes teh second step of glycolysis?
aldolase which is a lyase
F-1,6-BP to DHAP and GAP
What acts as a positive effector on pyruvate carboxylase and stimualtes gluconeogenesis?
Acetyl CoA
Pyruvate->oxaloacetate
What acts as a positive effector on PFK-1 that stimulates glycolysis?
Fructose 2,6, BP
What acts as a negative effector on PFK-1 that inhibits glycolysis?
Citrate
What acts as a negative effector on hexokinase that inhibits glycolysis?
Glucose 6-P
What is the effector outcome of ATP on aspartate carbamoylase?
Positive effect that stimulates pyrimidine synthesis
What is the effector outcome of CTP on aspartate carbamoylase?
Negative effectors that stimulate and inhibit pyrimidine synthesis
What are isoenzymes used to diagnose myocardial infarction?
LDH-1
CK-MB
Troponin
AST/SGOT1
