Amino Acids- Versatile Precursors Flashcards
Glycine s a precursor for what molecules?
creatine, heme and purine bases
Creatine synthesis involved which AAs?
glycine and arginine
What are the steps of synthesis of creatine?
In the kidney, glycine and arginine are combined to form guandinoacetate, then in the liver SAM donates a methyl group (methyl donor) to form creatine which then goes to the brain, heart and skeletal muscle
What does creatine kinase do?
present in the brain, heart, and skeletal muscle and converts creatine to creatine phosphate (which is the storage form of high energy phosphates in the body!!).
You can convert creatine phosphate to creatine to make ATP from ADP. It is better to store the phosphates in creatine phosphate rather than ATP because ATP is a massive regulator of processes in the body
Is creatine phosphate stable or unstable?
unstable. It often spontaneously forms creatinine which is excreted in urine
high plasma creatinine is a measure of kidney disorder
How can creatine phosphate and creatine kinase be used as diagnostic markers?
high plasma creatine kinase is an indicator of myocardial infarction and strokes (isozymes distinguish between muscle and heart CK)
creatine phosphate is a good marker for muscle disorders
What are the precursors for heme synthesis?
glycine and succinyl CoA (long pathway- don’t worry about knowing)
Defects along the heme synthesis pathway can lead to what?
porphyrias due to buildup of porphoryin intermediates- main effects are on CNS and skin (light sensitivity)- origin of vampire folklore
How is histamine made?
derived from histidine using PLP
What does histamine do?
vasodilation and increased permeability of vascular walls (leads to runny nose and watery eyes)
in the brain it acts an excitatory neurotransmitter (so antihistamine make you drowsy)
Tyrosine is a precursor for what?
catecholamines (dopamine, epi, and norepi), melanin (pigment) , and the hormones T4 and T3
What are the steps of catecholamine synthesis?
1) start with phenylalanine which is converted to tyrosine using BH4
2) tyrosine is hydroxylated using BH4 (tetrahydrobiopterin) to form dopa via tyrosine hydroxylase (RATE LIMITING STEP)
made in adrenal gland and in neurons:
3) Dopa is decarboxylated to dopamine using PLP
4) dopamine is hydroxylated to form norepinephrine using O2, vitamin C, and Cu2+
5) norepinephrine is converted to epinephrine via SAM
How is melanin formed?
tyrosine is made from Phe using BH4, and tyrosine is converted to melanin in melanocytes via tyrosine hydroxylase (a different one than the one used in catecholamine synthesis)
(defects cause albinism)
Tyrptophan is a precursor for what?
melatonin (regulates circadian rhythm) and serotonin (regulates mood control and appetite- low serotonin= increased depression or increased appetite)
What is arginine a precursor for?
nitric oxide. NO is given off during conversion of arginine to citrulline (rxn requires NADPH and O2)
NO causes vasodilation
