Brs Biochem 11/23

Front 1

Set 11 Q: This disease is marked by the accumulation of branched-chained amino acids (valine, isoleucine, and leucine) due to a defect in the oxidative decarboxylation steps of catabolism of these amino acids.

Back 1

Maples Syrup urine Disease - results in the accumulation of metabolites in the urine, imparting an odor of burnt sugar or maple syrup and leading to the development of neurological impairment and mental retardation - branched chain amino acids are broken down by alpha-keto acid dehydrogenase (which requires thiamine, coenzyme A, FAD, NAD, lipoate and pyrophosphate). Tx= thiamine

Front 2

Set 11 Q: This disorder results from a defect in the enzyme tyrosinase, with deficiency in the production of melanin from tyrosine

Back 2

Albinism - the lack of melanin results in loss of pigmentation of the skin, hair, iris, and retina with increased sensitivity to bright light, increased likelihood of sunburn and the development of skin cancer - can results from lack of migration of neural crest cells

Front 3

Set 11 Q: This neurotransmitter is produced by the decarboxylation of histidine and is important in acid secretion and the allergic response

Back 3

Histamine - binding of Histamine to H1 receptors in the stomach stimulates the release of gastric acid. Binding of histamine to H2 receptors on basophils stimulates the release of inflammatory mediators of the allergic response. - increasing mast cells or basophils increases histamine and therefore gastric acid production

Front 4

Set 11 Q: This amino acid is the principal excitatory neurotransmitter in the brain and spinal cord

Back 4

Glutamic acid (glutamate) - the drugs of abuse, such as ketamine and phencyclidine (PCP) antagonize glutamate neurotransmission.As well, memantine, the recently developed drug for Alzheimer's disease interferes with glutamate neurotransmission.

Front 5

Set 11 Q: This neutral amino acid functions as an important inhibitory neurotransmitter in the brainstem and spinal cord

Back 5

Glycine - the actions of this neurotransmitter are antagonized by the rodenticide strychnine, exposure to which leads to twitching and muscle spasms.

Front 6

Set 11 Q: This enzyme, located in the mitochondria catalyzes the first reaction of the urea cycle. It produces carbamoyl phosphate from NH4+, CO2, and 2 ATP.

Back 6

Carbamoyl phosphate synthetase I - a hereditary deficiency of this enzyme results in the inability to dispose of nitrogenous waste. Without strict dietary control, increased ammonia levels can lead to brain damage, coma, death.

Front 7

Set 11 Q: This enzyme of the urea cycle, located in the mitochondria, forms citrulline from ornithine and carbamoyl phosphate

Back 7

Ornithine transcarbomylase (OTC) -the citrulline that is produced is transported into the cytosol for completion of the urea cycle. Without dietary control, a genetic deficiency of OTC leads to neurologic impairment and potential death due to ammonia accumulation - Tx: arginine, which can carry and excrete 2 "waste" nitrogens in the urine

Front 8

Set 11 Q: This terminal enzyme of the urea cycle cleaves arginine to form urea and regenerates ornithine for a subsequent round of the cycle

Back 8

Arginase - a deficiency of this enzyme, unlike other enzymes of the urea cycle, does not result in the buildup of ammonia as arginine can be excreted in the urine, carrying with it two waste nitrogens. A benign disease

Front 9

Set 11 Q: This enzyme degrades asparginine to NH4+ and aspartate, which are further transaminated to oxaloacetate.

Back 9

Asparginase - the malignant cells in acute lymphoblastic leukemia (ALL) are unable to produce asparagine. Recombinantly produced asparaginase is given to such patients to further rob the leukemic cells of circulating asparagine

Front 10

Set 11 Q: This vitamin B12 requiring enzyme normally converts methymalonyl CoA to succinyl coA with accumulation of the precursor propionyl CoA, formed by the catabolism of isoleucine, threonine, and methionine.

Back 10

Methylmalonyl CoA mutase - if not controlled by strict dietary restrictions, the resultant disease, methymalonyl acidemia, causes failure to thrive, vomiting, dehydration, developmental delay, and seizures - high levels of methylmalonic acid will cause abnormal myelin. The same problems are seen with B12 deficiency.