AMino acid breakdown Flashcards
in what form does the liver give protein to muscle
- BCAA
- NH3 ends up as glutamine or alanine and made into urea
what is the first organ to metabolize aa’s after they have been absorbed in the gut
- liver
- low in BCAA transferases therefore can not utilize BCAA’s
how does the periportal hepatocytes vs the perivenous hepatocytes use ammonia?
- 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)
the cahill cycle
- 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
how is glutamine used by the intestine, what maintains glutamine?
-another organ that uses glu
- 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
what is glutamine used for in the kidney
-to produce NH4 in times of acidosis
what amino acids are made into pyruvate?
- alanine
- serine
- cysteine
what do dehydratases produce when acting on aa’s
-ketoacids
once an amino acid is made into pyruvate, what can it be made into?
glucose
what can ketobuterate be made into?
glucose via succinyl coa
glutamate can be intervonverted to what using what (enzyme and cofactor)?
- proline
- proline DH uses FAD
what aa’s can you not make glucose from
- leucine and lysine
- your blood glucose will not go up when these are broken down
where does the break down of amino acids occur
-in the mitochondria
components of what structure are upregulated in response to energy needs
-proteasome components
what amino acids are metabolized to acetyl-coa?
-what classification does this produce?
- lysine and leucine
- since their breakdown product can not be converted into glucose, these are termed ketogenic aa’s
what aa’s are broken down into alpha KG?
-proline, glutamine, arginine, and glutamate
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?
- 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
maple syrup urine disease
- occurs when people lack the branched chain alpha ketoacid dehydrogenase
- get a build up of ketoacids and have urine that smells like maple syrup
what amino acids are metabolized into acetyl coa?
- 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
the conversion of propionyl Coa to succinylcoa requires what cofactors (for both of the enzymes needed)
biotin and vitamin B12
what is the reaction catalyzed by methylmalonyl mutase and what can defects in this enzyme produce and how is it caused?
- 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
VB12 comes from, commonality of the def
- meat, fish, cheese, yeast
- required for the metabolism of valin, isoleucine, and methionine
- 3 to 40% of older adults have various degrees of def
what form of the VB12 is needed for the mutase reaction?
-how is the vitamin absorbed?
- adenosyl
- using intrinsic factor which is produced by the stomach
methylmalonic acidemia arises from…
- def of VB12,
- lack of intrinsic factor
- inability to convert VB12 to adenosyl form
- def in methylmalonyl coa mutase
what amino acids are metabolized into OAA
- 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
what amino acids are metabolized into fumerate and what is the common intermediate?
- tyrosine and phenylalanine
- homogentisate is the common intermediate
PKU
- cause
- coenzyme and what does the recylcing of it
- treatment
- symptoms
- 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
alkaptonuria
- characterization
- treatment
- phe disease
- dark urine due to def in homogentisic acid oxidase
- treatment: reduce phe and tyr
- vitamin c may retard conversion of homogentisate
tyr is made from?
- phe
- using the enzyme, phe hydroxylase which uses the cofactor tetrahidrobiopterin, converting it to dihydrobiopterin
- DHB reducatse recylces the cofactor
