Protein Metabolism II (Lecture 4 - Exam 3) Flashcards
Dietary proteins provide AAs, which are needed for what? (4 total)
(1) Muscle tissue
(2) Immune cell synthesis
(3) Plasma protein synthesis (keeps our blood in the proper osmolality and viscosity)
(4) Nitrogen containing non-protein compound synthesis
Creatine: what is it synthesized from?
Can be obtained from food, mostly meat and meat products
It is synthesized from arginine and glycine and then methylated by SAM
Why is creatine important?
It is the first line of energy used before muscle glycogen is broken down to produce ATP.
This allows someone who is going to do a quick sprint, to get energy more quickly than breaking down glycogen in muscle.
In what form is creatine activated?
ACTIVATE = PHOSPHORYLATED by CREATINE KINASE in the MITOCHONDRIA, which can now function to phosphorylate an ADP to form ATP. This ATP is going to be used when muscle contract.
INACTIVE = UNPHOS
Carnitine: what is it synthesized from?
Can be obtained from food, mostly in meat and meat products
It can also be synthesized from LYSINE
What 5 other nutritional factors does carnitine require for synthesis?
(1) SAM
(2) IRON
(3) PLP
(4) VITAMIN C
(5) NIACIN
What is the function of carnitine?
It helps with carrying the FAs across the MITO membrane and into the mito matrix to be oxidized through beta-oxidation.
What is glutathione made from?
3 AA + ATP
GLUTAMATE
CYSTEINE
GLYCINE
What is the function of glutathione?
Acts as a scavenger of free radicals, protects against oxidation and damage
Which form of glutathione is reduced?
GSH
Which form of glutathione is oxidized?
GSSG
Glutathione peroxidase
Catalyzes the reaction of H202 (hydrogen peroxide) is degraded to H20.
Note this is SELENIUM dependent
Glutathione reductase
The enzyme that reduces GSSG to GSH via NADPH as the reducing agent
Histamine
Part of the inflammatory response of allergies
It is also partly involved in digestion, as histamine STIMULATES gastric acid secretion and can STIMULATE vasodilation
Histidine decarboxylase
Enzyme that decarboxylates HISTIDINE —-> HISTAMINE
This enzyme is PLP dependent
What is essential for serotonin biosynthesis?
TRYPTOPHAN
What are 2 functions of serotonin?
(1) 90% located in the intestinal cells where it stimulates mobility.
(2) 5% Located in the CNS where it acts as a neurotransmitter
Which side of the intestine secrete serotonin?
BOTH: basolateral & luminal side
Explain the conversion of tryptophan to serotonin.
(1) Tetrahydrobiopterin is used as a co-factor, and it is converted to dihydrobiopterin with the HYDROXYLASE enzyme and the addition of 02. The product is 5-Hydroxytryptophan.
(2) AROMATIC AMINO ACID DECARBOXYLASE enzyme (PLP/B6) converts 5-Hydroxytryptophan to serotonin.
Catecholamines
Includes dopamine and norepinephrine
REMEMBER: TYROSINE is the “parent compound”
Epinephrine
synthesized from the methylation of norepinephrine in the ADRENAL GLAND
Which compounds are released in response to emotional stimulation?
NOREPINEPHRINE & EPI
“Fight or Flight” response
Can also be released during times of low glucose or very cold temperatures
What is required for the biosynthesis of catecholeamines from tyrosine?
- PLP
- VITAMIN C
- COPPER
- SAM
Explain the pathway of catecholeamine biosynthesis.
(1) Tetrahydrobiopterin + O2 are utilized by the enzyme TYROSINE HYDROXYLASE. This converts tyrosine to L-Dopa.
(2) L-Dopa is decarboxylated, in a PLP-dependent reaction, which forms DOPAMINE.
(3) DOPAMINE HYDROXYLASE adds another hydroxyl group, forming NOREPINEPHRINE.
(4) SAM adds a methyl group to norepinephrine, forming epinephrine.
What is porphyrin synthesized from?
Glycine (non-essential AA)
How is glycine synthesized?
Glycine is considered non-essential AA because it can be biosynthesized from SERINE. Which can be synthesized from 3-phosphoglycerate (which is formed from glycolysis when glutamate donates it’s amino group to serine)
Explain porphyrin synthesis.
Glycine and succinyl CoA combine (requires PLP/B6) to form ALA (alpha aminolevulinic acid) which will go on to form porphyrin
What is the most abundant form of porphyrin?
HEME
Remember: Iron binds to the middle of the molecule, which is how oxygen is carried to the peripheral tissues.
Where is heme found?
Hemoglobin
Myoglobin
Cytochromes (ETC)
P450 enzymes
Catalase
Nitric oxide synthase and peroxidase
What AA is needed for histamine synthesis?
HISTIDINE
