Page 5 - Synthesis of Epinephrine & Regulation of Catecholamines Flashcards
The starting substrate for EPI and NEPI is
L-tyrosine
The first enzyme used is _ and _ is converted to _
tyrosine hydroxylase, L-tyrosine, L-DOPA
L-DOPA is converted to _ by the enzyme _
Dopamine, Aromatic L-amino acid decarboxylase
Dopamine is converted into _ by _
NEPI, dopamine beta-hydroxylase
NEPI is converted to _ by _
EPI, PNMT
Catecholamines are very physiologically influential so they are
tightly regulated
Methods of Regulation of Catecholamines
enzyme activity & expression levels, bioavailability, tissue-specific expression of a and b adrenergic receptors
An example of regulation of enzyme activity and expression is PNMT, PNMT is the enzyme that catalyzes the reaction from NEPI to EPI. Different types of _ can affect PNMT _, _ _ and _ _
stressors, mRNA, protein expression, enzyme activity
Catecholamine bioavailability is regulated by different plasma binding proteins such as
Albumin
When catecholamines are bound by a plasma binding protein they are
unable to interact with adrenergic receptors and exert physiological effects
What percentage of catecholamines in humans are unbound in the blood stream and are bioavalible
50%
Bioactivity of catecholamines is short-lived. What is the half life of catecholamines?
minutes
Why is the bioactivity of catecholamines so short lived?
Specific enzymes can quickly inactivate them
Which specific enzymes can quickly inactivate catecholamines?
catechol-O-methyltransferases, monoamine oxidases
