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Biochemistry MBS > AMino acid breakdown > Flashcards

AMino acid breakdown Flashcards

1
Q

in what form does the liver give protein to muscle

A
  • BCAA

- NH3 ends up as glutamine or alanine and made into urea

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2
Q

what is the first organ to metabolize aa’s after they have been absorbed in the gut

A
  • liver

- low in BCAA transferases therefore can not utilize BCAA’s

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3
Q

how does the periportal hepatocytes vs the perivenous hepatocytes use ammonia?

A
  • periportal uses NH4 to create carbamoyl phosphate via CPS1 which feeds into the urea cycle
  • Perivenous hepatocytes use the excess NH4 to make glutamine using glutamine synthase
  • therefore little or no ammonia ever leaves the liver (unlike the intestine)
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4
Q

the cahill cycle

A
  • important for transport in the body of alanine to the liver for disposal in the body
  • alanine is sent to liver and is converted using alphaKG to make pyruvate and glutamate
  • glutamate is relieved of its NH4 which is then excreted as urea
  • pyruvate is converted to glucose and sent back to the muscle
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5
Q

how is glutamine used by the intestine, what maintains glutamine?
-another organ that uses glu

A
  • intestines use it for fuel
  • clinically, a glu solution can be used to promote G tract healing and nutritional supplementation with GI disorders, HIV/AIDS, cancer and other clinical illneses
  • liver maintains the glu levels, in particular the perivenous hepatocytes
  • kidneys also use glu for ammonia production using the glutaminase reaction, especially when pH control is needed
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6
Q

what is glutamine used for in the kidney

A

-to produce NH4 in times of acidosis

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7
Q

what amino acids are made into pyruvate?

A
  • alanine
  • serine
  • cysteine
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8
Q

what do dehydratases produce when acting on aa’s

A

-ketoacids

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9
Q

once an amino acid is made into pyruvate, what can it be made into?

A

glucose

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10
Q

what can ketobuterate be made into?

A

glucose via succinyl coa

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11
Q

glutamate can be intervonverted to what using what (enzyme and cofactor)?

A
  • proline

- proline DH uses FAD

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12
Q

what aa’s can you not make glucose from

A
  • leucine and lysine

- your blood glucose will not go up when these are broken down

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13
Q

where does the break down of amino acids occur

A

-in the mitochondria

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14
Q

components of what structure are upregulated in response to energy needs

A

-proteasome components

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15
Q

what amino acids are metabolized to acetyl-coa?

-what classification does this produce?

A
  • lysine and leucine

- since their breakdown product can not be converted into glucose, these are termed ketogenic aa’s

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16
Q

what aa’s are broken down into alpha KG?

A

-proline, glutamine, arginine, and glutamate

17
Q

what amino acids are metabolized to succinyl coa?

  • what is the common intermediate between all of them?
  • these amina acids are broken down where?
  • what do the ketoacids from these aa’s need in order to be metabolized?
  • what type of enzyme creates the ketoacid intermediates of these enzymes?
A
  • threonine, methionine, isoleucine, and valine
  • propionyl coa is a common intermediate, it is made by BCAA dehydrogenases
  • these are BCAA’s therefore they are used in the muscle
  • thiamine, lipoate, and FAD
  • aminotransferases
18
Q

maple syrup urine disease

A
  • occurs when people lack the branched chain alpha ketoacid dehydrogenase
  • get a build up of ketoacids and have urine that smells like maple syrup
19
Q

what amino acids are metabolized into acetyl coa?

A
  • lysine and leucine
  • leucine is a BCAA and is first made into a ketoacid and then converges to form HMG-coa which is then made into acetyl coa
  • isoleucine is also made into acetyl-coa but without first forming HMG-coa
20
Q

the conversion of propionyl Coa to succinylcoa requires what cofactors (for both of the enzymes needed)

A

biotin and vitamin B12

21
Q

what is the reaction catalyzed by methylmalonyl mutase and what can defects in this enzyme produce and how is it caused?

A
  • converts methylmalonyl coa (made from propionyl coa from the metabolism of BCAA’s) into succinyl coa
  • this produces methylmalonate in the urine
  • caused by missing enzyme, VB12 def, VB12 absorption problems, or VB12 processing problems
22
Q

VB12 comes from, commonality of the def

A
  • meat, fish, cheese, yeast
  • required for the metabolism of valin, isoleucine, and methionine
  • 3 to 40% of older adults have various degrees of def
23
Q

what form of the VB12 is needed for the mutase reaction?

-how is the vitamin absorbed?

A
  • adenosyl

- using intrinsic factor which is produced by the stomach

24
Q

methylmalonic acidemia arises from…

A
  • def of VB12,
  • lack of intrinsic factor
  • inability to convert VB12 to adenosyl form
  • def in methylmalonyl coa mutase
25
Q

what amino acids are metabolized into OAA

A
  • asparagine is made into aspartate which is made into OAA

- the NH4 of aspartate is passed to alpha KG to make glutamate in a aminotransferase reaction

26
Q

what amino acids are metabolized into fumerate and what is the common intermediate?

A
  • tyrosine and phenylalanine

- homogentisate is the common intermediate

27
Q

PKU

  • cause
  • coenzyme and what does the recylcing of it
  • treatment
  • symptoms
A
  • could be from enzymatic def in phenylalanine hydroxylase
  • could also be from def in the ability to recycle tetrahydrobiopterin which is a cofactor used by phenylalanine hydroxylase (recylcing done by DHB reductase)
  • treatment: low phe diet, supplements tyrosine, perhaps supp a coenzyme, monitor serum levels of phe, referral to parent support group
  • musty urine
  • if left unteated, the IQ of the chile will steadily decrease
28
Q

alkaptonuria

  • characterization
  • treatment
A
  • phe disease
  • dark urine due to def in homogentisic acid oxidase
  • treatment: reduce phe and tyr
  • vitamin c may retard conversion of homogentisate
29
Q

tyr is made from?

A
  • phe
  • using the enzyme, phe hydroxylase which uses the cofactor tetrahidrobiopterin, converting it to dihydrobiopterin
  • DHB reducatse recylces the cofactor

Biochemistry MBS (36 decks)

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