protein metabolism

Question 1

Collagen is the most abundant protein in human body that forms a triple-stranded helix, which is comprised of both ___________ and ___________

Answer 1

hydroxyproline (Hyp) and hydroxylysine (Hyl)

Question 2

Hydroxyproline serves what function in collagen

Answer 2

used in collagen for H-bonding that increases collagen strength

Question 3

_____ converts Proline to Hydroxyproline

Answer 3

Prolyl hydroxylase

Question 4

what function does hydroxylysine (Hyl) serve in collagen?

Answer 4

used in collagen for interchain cross-links

Question 5

________ converts Lysine to Hydroxylysine

Answer 5

Lysyl hydroxylase

Question 6

____________ and _________ rely on Vit-C (ascorbate) as coenzyme, thus, lack of Vit-C leads to Scurvy (i.e. reduced collagen strength).

Answer 6

Prolyl hydroxylase,

Lysyl hydroxylase

Question 7

__________________ converts Glutamate to g-Carboxyglutamate (Gla), which is Vit-K dependent.

Answer 7

G-glytamyl carboxylase

Question 8

Describe the Ubiquitin-proteasome system, a type of intracellular protein breakdown pathway.

Answer 8

ATP dependent that is used to cross-link protein to ubiquitin. Ubiquitinated proteins are then sequestered to the proteasome (i.e. a giant cellular trashcan that has proteolytic activity to break down proteins).

Question 9

describe the Lysosomal pathway, which is a type of intracellular protein breakdown pathway.

Answer 9

ATP independent that is used primarily to “engulf” extracellular proteins (or even live pathogens). Proteins are broken down by acid hydrolysis and other lysosomal proteins (i.e. cathepsins).

Question 10

what are Aminotransferases?

Answer 10

enzymes that transfer amino groups (nitrogen movers)

Question 11

Ultimately for protein degradation, aminotransferases move nitrogen to _____ and _______ which are the molecules that carry nitrogen into the Urea Cycle where ultimately the nitrogen winds up on urea which is excreted in the urine.

Answer 11

aspartic acid (Asp),
ammonia

Question 12

What are two entry points for Nitrogen in the urea cycle:

Answer 12

1) Apartate.

2) Free ammonia (incorporated into carbamoyl phosphate)

Question 13

_______ is an allosteric activator of Carbamoyl phosphate synthetase I.

Answer 13

N-acetylglutamate

Question 14

______ is an activator of N-acetylglutamate synthase, which catalyzes the following reaction:
acetyl CoA + glutamate to N-acetylglutamate

Answer 14

Arginine

Question 15

Most tissues use ________ to convert glutamate to glutamine for transport to the liver (to enter the urea cycle).

Answer 15

glutamine synthetase

Question 16

_____ converts arginine to citrulline to produce NO, an important molecule used as a neurotransmitter and vasodilator

Answer 16

NO synthase

Question 17

Branched Chain Amino Acids include _________

Answer 17

leucine, valine, and isoleucine

Question 18

what is Maple Syrup Urine Disease (MSUD)

Answer 18

Occurs when branched-chain alpha-ketoacid dehydrogenase complex is deficient and there is consequently a buildup of the alpha-keto acids in urine (“sweet smelling”).

Question 19

________ is used to make T4 (prohormone) that is converted to T3 (hormone).

Answer 19

Tyrosine

Question 20

Thyroid stimulating hormone (TSH): Stimulates _____ uptake and stimulates release of T4 andT3.

Answer 20

iodide (I-)

Question 21

What does Thyroid peroxidase do?:

Answer 21

Oxidizes iodide (I-) to (I2).

Question 22

what is Thyroglobulin (Tg)

Answer 22

Contains Tyr residues iodinated to form T4 andT3.

Question 23

what does Thyroxin binding globulin (TBG) do?

Answer 23

Transports T4 andT3.

Question 24

Creatine phosphate and ornithine are derived from ______

Answer 24

Arginine

Question 25

which 2 amino acids contain sulfur

Answer 25

methionine and cystiene

Question 26

what is Hyperhomocysteinemia? .

Answer 26

elevated levels of homocysteine cause multiple problems that include cardiovascular disease

Question 27

what can cause Hyperhomocysteinemia?

Answer 27

Results from low levels of folate, B6, & B12 (vascular disease)

Question 28

What is Homocystinuria: . Leads to mental retardation, osteoporosis, & vascular disease

Answer 28

results from defect in cystathionine-b-synthase (CBS), so that homocysteine cannot be converted to cystathionine (and eventually cysteine).

Question 29

What is the presentation of Homocystinuria

Answer 29

mental retardation, osteoporosis, & vascular disease.

Question 30

What is Cysteinuria?

Answer 30

Due to a defect in the transporter of cysteine (& Ornithine, Lysine, Arginine) that leads to crystallization in urea -> kidney stones (renal failure)

Question 31

how do you treat Cysteinuria

Answer 31

acetazolamide (makes cysteine more soluble)

Question 32

what are the 3 functions of Glutathione (GSH)

Answer 32

i) thiol acts as redox buffer (“SH buffer”) to maintain proteins in their reduced forms (i.e. intracellular proteins) and regulate activity (i.e. enzymes)
ii) Cofactor for several enzymes (i.e. Glutathione transferase, GST).
iii) Reduce hydrogen peroxide (H2O2) to water and general protection against ROS (radical oxidizing species).

Question 33

Trp is used to produce

Answer 33

serotonin (neurotransmitter), melatonin (hormone), and niacin (energy).

Question 34

Trp is metabolized to ___________ .

Answer 34

pyruvate or acetyl-CoA

Question 35

Phe, Tyr are metabolized to _________

Answer 35

fumarate or acetoacetate

Question 36

Phe is hydroxylated by phenylalanine hydroxylase to produce ______ using ______ cofactor

Answer 36

Tyr,

BH4

Question 37

Tyr is hydroxylated by tyrosine hydroxylase to produce DOPA using BH4, which is subsequently metabolized to: ________

Answer 37

1) Catecholamines, which include DOPA, dopamine, norepinephrine, epinephrine.
2) Melanin, which is a pigment produced as a complex combination of several molecules derived from Tyrosine metabolism.

Question 38

what is Phenylketonuria (PKU)?

Answer 38

A defect in phenylalanine hydroxylase that leads to build-up of alternative byproducts (phenylactate, phenylacetate, and phenylpyruvate).

Question 39

Porphyrins such as Heme are cyclic molecules made of ________ primarily produced in liver

Answer 39

4x pyroles

Question 40

Porphyrins bind ________.

Answer 40

Fe2+ (iron)

Question 41

________ are the general term for diseases in porphyrin synthesis

Answer 41

Porphyrias

Question 42

Lead inhibits two enzymes in porphyrin synthesis ____________ ”lead poisining”.

Answer 42

(delta-Aminolevulinate dehydratase, ferrochelatase)