hormondr ervan

8/7/2019 hormondr ervan

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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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(triiodothyronine)

(Serotonin)


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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(triiodothyronine)

(Serotonin)


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?

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