Biochem Weight Loss Peptide Hormones

Front 1

What are the four glycoprotein hormones ('typical'synthesis)and what do they all activate

Back 1

TSH LS FSH CG
all activate adenyl cyclase

Front 2

What are the structural features of glycoprotein hormones and what are their activities

Back 2

alpha chain: same in all glycoprotein hormones, activates adenyl cyclase,

Beta chain: different across hormones, amount of hormone dictated by beta chain

each chain arose from different genes

Front 3

insulin and angiotensin are two examples of cleavage of peptides to get hormones(prepro->pro->H) describe biochemically the cleavage of insulin

Back 3

cleave proinsulin at positively charged lys and arg residues


first you do a trypsin like cleavage at the carboxy terminal side of the basic amino acids(lys/arg). Then you cleave off the carboxy at the newly formed end using CARBOXYPEPTIDASE B-like enzyme. Proinsulin is packaged into golgi where removal of c peptide begins in golgi(trans)

Front 4

Familial cholesterimia and insulin

Back 4

secrete equal amounts of insulin and proinsulin(usually secreted at about 5%), but apparently normal with respect to glucose metabolism

Front 5

POMC is an example of what type of hormone?

Back 5

a polyprotein hormone. Makes ACTH, beta-lipoprotein

Front 6

POMC gets cleaved in the anterior lobe to what?

Back 6

ACTH (and side product beta LPH)

Front 7

POMC gets cleaved to what in the neurointermediate lobe?

Back 7

POMC -> ACTH -> alpha MSH and CLIP

POMC-> beta LPH ->gamma LPH and beta-END

POMC -> N-term -> gamma MSH and J

Front 8

Polypeptide hormones can make what type of product?
3 different scenarios

Back 8

1) products with different aa seq and unrelated activites
2) products with related aa seq and sometimes function
3) multiple repeats of aa seq giving identical copies

Front 9

Is POMC mono or poly cistronic

Back 9

Still mono cistronic
a single polypeptide chain will result from mRNA translation, after translation when you have the peptide, THEN you cleave it to ACTH/B-LSH

in contrast to polycistronic mRNA, where translations will yield several polypeptides.

Front 10

cleavage of POMC: early cleavage is the same in both ant lob and neurointermediate lobe.
but additional cleavage occurs in the intermediate lobe due to the prescence of enzymes not in the adenohypophysis

Back 10

sdhf

Front 11

POMC post translational modifications

Back 11

glycosylation, phosphorylation and alpha amidation

they are common features of neuropeptide hormones and are often essential for activity

Front 12

what is the characteristic post translational modification of neuropeptide hormones

Back 12

alpha amidation
ex) ACTH--> alhpa-MSH

mechanism:
1)'typical' cleavage b/w basic aa's(endopeptidase then carboxypeptidase B-like enz)

2) removal of c-terminal basic aa

3)oxidation of C terminal glycine by PAM (peptidyl glycine alpha-amidating monooxygenase) to give an amide(NH2) at the end instead of glycine coo-

Front 13

why is hyperpigmentation of the skin seen in addisons disease

Back 13

insufficiency of the adrenal cortex means ACTH isn't inhibited so you have large amounts of it being produced. Since MSH and ACTH come from POMC, msh gets made too??? SEE [age 84

Front 14

What is the example of a polyprotein cleaved to produce multiple copies of the same protein

Back 14

opiod-like enckephalins
M1-M6 = Met-enkephalin
L = Leu-enkephalin

Front 15

Transcriptional control of ACTH and LPH synthesis in the anterior pituitary

Back 15

Soluble cortisol-receptor complex translocates into the nucleus and exerts a primary effect

POMC mRNA is increased by CRH and adrenalectomy

POMC mRNA is decreased by glucocorticoids

Front 16

Transcriptional control of alpha -MSH, gamma-MSH, and beta-endorphins in the neurointermediate lobe

Back 16

mRNA is inhibited by dopaminergic neurons, and stimulated by dopaminergic antagonists
mechanism is unknown

Front 17

Describe the effects of MSH

Back 17

MSH binds to Melanocortin-4 receptors on neurons and these neurons suppress appetite.

Front 18

describe the effects of leptin

Back 18

leptin is secreted by adipocytes and binds pomc neurons through it's receptor leading to alpha-MSH secretion, MSH suppresses appetite, thus a large amount of fat suppresses appetite

leptin also activates AMP kinase which inhibits acetylCoA carboxylase. Inhibition of acetylcoa carboxylase(makes malonyl CoA) increases FA mobilization

Front 19

what does Haloperidol do

Back 19

it is a dopamine antagonist that stimulates POMC-->alpha/gamma-MSH and beta endorphins

Front 20

what are the consequences of low POMC

Back 20

low POMC means low MSH which means increased appetite and weight gain with altered lipid metabolism (wt gain out of proportion to food intake)

Front 21

Explain differential processing of mRNA precursors

Back 21

its a mechanism for producing different products from a single gene, it's what helps explain some cases of tissue differences

Front 22

explain the relationship between calcitonin and calcitonin gene-related peptide (CGRP

Back 22

they are produced from the sa,e gene in different tissues through

Alternative splicing:
Thyroid C-cells = calcitonin
Neurons = CGRP(migraines)

Front 23

What are the examples of
Post translational
Post transcriptional
processing discussed so far

Back 23

translational - POMC
transcriptional - CGRP(splice choice)

Front 24

what is special about thyroxine?

Back 24

is is cleaved from a large precursoe, but is a modified amino acid

Iodo-Tg -->(cathepsin) T4-gln T3-Gln + aa --> (dipeptidase) T4/T3