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Hormone Biochemistry, Hormone Biochemistry, Synthesis & ReleaseSynthesis & Release
(Serotonin)
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Biosynthesis and secretion of polypeptide
Biosynthesis and secretion of steroid ormones Hormone transport mechanisms
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How are hormone How are hormone syn es ze n en ocr ne syn es ze n en ocr ne
cells and tissues?cells and tissues?
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Amino Acid Derivatives
, indoleamines and thyroid hormones are
These hormones are small in molecular size Some are ipi so u e t yroi ormones , while others are lipid insoluble (serotonin,
me aton n, ep nep r ne
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The Catecholamines: opam ne, ep nep r ne and norepinephrine
a catecholunsa ura e s xcar on r ng
Dopamine, epinephrine (adrenaline), and norepinephrine (noradrenaline) are derived from the amino acid
tyrosine and are released into circulation to have endocrine functions
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The Indolamines: Indolamines are derived from the amino acid tryptophan
sero on n an melatonin
MAO enzyme
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The Indolamines: sero on n an
melatonin
Monoamine oxidase(MAO) enzymes are key in the conversion
the inactive 5HIAA. This is why MAO
used as antidepressant drugs
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tyrosine Thyroid Hormone Synthesis
Begins with the amino acid tyrosine
3monoiodotyrosine (MIT) 3,5diiodotyrosine (DIT)
triiodothyronine (T 3)
reverse T3 (rT3)
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Amino Acid Derivatives Summary
Includes: catecholamines (epinephrine, norepinephrine) indoleamines (serotonin, melatonin) yro ormones ,
These hormones are all formed by modifications to
Tyrosine (catecholamines, thyroid hormones) Tr to han indolamines
Some are lipid soluble (thyroid hormones), while others are lipid insoluble (serotonin, melatonin, epinephrine)
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Hormone Biochemistry
Not all hormones are the same!Types o Hormones:
(triiodothyronine)
(Serotonin)
Amino acid derivatives Polypeptide hormones
Steroids Fatty acid derivatives(i.e., prostaglandins)
(Testosterone)
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An example of a polypeptide hormone:
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Protein Hormone Synthesis Transcription RNA synthesis
rom Post transcriptional modification:
form mRNA from excision and
splicing
Translation assembly of amino acids via specific base airin of the anticodons of the carrier amino ac lated
transfer RNAs to the correspond codons of the mRNA (creation of the polypeptide chain)
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Gene Transcription (DNA RNA)RNA polymerase (RNAP)
Step 1
Step 2
Step 3
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Gene Translation (mRNA Polypeptide Protein)
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T es of Pe tide Hormone mRNAs Most polypeptide hormones are transcribed as a
prepro ormone m a as a s gna pep e attached. This signal peptide is cleaved as the protein hormone is translated and translocated across the rou h endoplasmic reticulum (RER) membrane.
prohormone protein that are precursors to the active molecule. The prohormone is converted into the active
hormone within the cell where it is produced, in the blood, or in target tissues. Note that many
hormone.
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Preprohormones:convers on to act ve ormones
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Functions of a prohormone:
1) Further proteolytic processing in some cells may produce
depends on cell type2) May facilitate transport and sorting in cell3) May facilitate folding of the molecule
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Prohormone postranslational processing can be
,
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Polypeptide Hormones Show High Variation in Amino Acid Structure among Taxa
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Hormone Biochemistry
Not all hormones are the same!Types o Hormones:
(triiodothyronine)
(Serotonin)
Amino acid derivatives Polypeptide hormones
SteroidsFatty acid derivatives
(i.e., prostaglandins)
(Testosterone)
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Steroid Hormone Synthesis
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Pathways of Steroid Hormone Synthesis
(See Handout)
stress res onsesNa +/water
sex differencesin phenotype
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Steroid Synthesis Summary Handout
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Steroid HormoneSynthesis
Take-home point 1:
Steroid synthesis begins withthe conversion of cholesterolto pregnenolone
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Steroid HormoneSynthesis
Take-home point 2:
Corticosteroids, androgens andestrogens are all generated
from the same precursor(pregnenolone) through
conversion enzymes
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Tissue and cell variation in expression of conversion enzymes determines tissue and cellspecific steroidogenesis
Regulation of steroidogenesiscan occur by up or down regulating
enzymesDifferences in
steroidogenesispathways b/w gonads and adrenal cortex
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Steroid Hormone Synthesis
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Characteristics of Steroid Hormones (and Thyroid Hormones)
Non polar, lipid soluble
Usually bind to protein receptors in the
recent evidence for membrane steroid receptors
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Hormone Biochemistry
Not all hormones are the same!Types o Hormones:
(triiodothyronine)
(Serotonin)
Amino acid derivatives Polypeptide hormones
SteroidsFatty acid derivatives
(i.e., prostaglandins)
(Testosterone)
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Essential Fatty Acid Substrate Derivate
ormones cosano s
Prostaglandin E1(regulate vasotconstriction/dilation;
Thrombaxane A2(regulate inflammation)
Leukotriene B4(regulate inflammation)
Juvenile Hormone 3(regulates insect development )
There are over 20 pathways for conversion of essential fatty acids to hormones
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There are over 20 pathways for conversion of essential fatty acids to hormones Fatty acids compete for enzyme availability Ome a-3 fatt acid derivatives lessen inflammation caused b ome a-6 fattacid derivates
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Low dietary intake of less inflammatory essential
a y ac s suc as mega as een n e o inflammation related diseases and perhaps even mental illnesses.
Increased dietary Omega 3 helps prevent cardiovascular disease, hypertension, rheumatoid arthritis and can ease symptoms in psychiatric disorders
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4 types of hormones:
Amino acid derivatives Polypeptide hormones coded by genes ero ormones c o es ero er ve Lipid derived
These hormone differ in mechanisms for synthesis and regulation
The biochemical properties (polarity, lipophilicity) vary widely Implications for transport and mode of action on cells
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Lecture Questions
1) What are the major classes of hormones, andhow do the differ?
2) How are polypeptide hormones synthesized?
3) How are steroid hormones synthesized? What
re ulates tissue-s ecific s nthesis of steroids?4) Why is there so much variation among taxa in
,among steroid hormones or amino acidderivative hormones?