Entry of Aspartate into the Urea Cycle This is the second nitrogen-acquiring reaction.
-
date post
21-Dec-2015 -
Category
Documents
-
view
218 -
download
0
Transcript of Entry of Aspartate into the Urea Cycle This is the second nitrogen-acquiring reaction.
![Page 1: Entry of Aspartate into the Urea Cycle This is the second nitrogen-acquiring reaction.](https://reader035.fdocuments.in/reader035/viewer/2022081514/56649d545503460f94a318b4/html5/thumbnails/1.jpg)
![Page 2: Entry of Aspartate into the Urea Cycle This is the second nitrogen-acquiring reaction.](https://reader035.fdocuments.in/reader035/viewer/2022081514/56649d545503460f94a318b4/html5/thumbnails/2.jpg)
![Page 3: Entry of Aspartate into the Urea Cycle This is the second nitrogen-acquiring reaction.](https://reader035.fdocuments.in/reader035/viewer/2022081514/56649d545503460f94a318b4/html5/thumbnails/3.jpg)
Entry of Aspartate into the Urea Cycle
• This is the second nitrogen-acquiring reaction
![Page 4: Entry of Aspartate into the Urea Cycle This is the second nitrogen-acquiring reaction.](https://reader035.fdocuments.in/reader035/viewer/2022081514/56649d545503460f94a318b4/html5/thumbnails/4.jpg)
Nitrogen-acquiring reactions in the synthesis of urea. In the reaction catalyzed by argininosuccinate synthetase, the second nitrogen enters from aspartate. Activation of
the ureido oxygen of citrulline in step 1 sets up the addition of aspartate in step 2.
![Page 5: Entry of Aspartate into the Urea Cycle This is the second nitrogen-acquiring reaction.](https://reader035.fdocuments.in/reader035/viewer/2022081514/56649d545503460f94a318b4/html5/thumbnails/5.jpg)
Aspartate –Arginosuccinate Shunt Links Urea Cycle and Citric Acid Cycle
![Page 6: Entry of Aspartate into the Urea Cycle This is the second nitrogen-acquiring reaction.](https://reader035.fdocuments.in/reader035/viewer/2022081514/56649d545503460f94a318b4/html5/thumbnails/6.jpg)
Not All Amino Acids can be Synthesized in Humans
• These amino acids must be obtained as dietary protein
• Consumption of a variety of foods (including vegetarian only diets) well supplies all the essential amino acids
![Page 7: Entry of Aspartate into the Urea Cycle This is the second nitrogen-acquiring reaction.](https://reader035.fdocuments.in/reader035/viewer/2022081514/56649d545503460f94a318b4/html5/thumbnails/7.jpg)
![Page 8: Entry of Aspartate into the Urea Cycle This is the second nitrogen-acquiring reaction.](https://reader035.fdocuments.in/reader035/viewer/2022081514/56649d545503460f94a318b4/html5/thumbnails/8.jpg)
Fate of Individual Amino Acids• Seven to acetyl-CoA
– Leu, Ile, Thr, Lys, Phe, Tyr, Trp
• Six to pyruvate– Ala, Cys, Gly, Ser, Thr, Trp
• Five to -ketoglutarate– Arg, Glu, Gln, His, Pro
• Four to succinyl-CoA– Ile, Met, Thr, Val
• Two to fumarate– Phe, Tyr
• Two to oxaloacetate – Asp, Asn
![Page 9: Entry of Aspartate into the Urea Cycle This is the second nitrogen-acquiring reaction.](https://reader035.fdocuments.in/reader035/viewer/2022081514/56649d545503460f94a318b4/html5/thumbnails/9.jpg)
Summary of Amino Acid Catabolism
![Page 10: Entry of Aspartate into the Urea Cycle This is the second nitrogen-acquiring reaction.](https://reader035.fdocuments.in/reader035/viewer/2022081514/56649d545503460f94a318b4/html5/thumbnails/10.jpg)
Some enzyme cofactors important in one-carbon transfer reactions
![Page 11: Entry of Aspartate into the Urea Cycle This is the second nitrogen-acquiring reaction.](https://reader035.fdocuments.in/reader035/viewer/2022081514/56649d545503460f94a318b4/html5/thumbnails/11.jpg)
![Page 12: Entry of Aspartate into the Urea Cycle This is the second nitrogen-acquiring reaction.](https://reader035.fdocuments.in/reader035/viewer/2022081514/56649d545503460f94a318b4/html5/thumbnails/12.jpg)
Conversions of one-carbon units on tetrahydrofolate
![Page 13: Entry of Aspartate into the Urea Cycle This is the second nitrogen-acquiring reaction.](https://reader035.fdocuments.in/reader035/viewer/2022081514/56649d545503460f94a318b4/html5/thumbnails/13.jpg)
Synthesis of methionine and S-adenosylmethionine in an activated-methyl cycle
![Page 14: Entry of Aspartate into the Urea Cycle This is the second nitrogen-acquiring reaction.](https://reader035.fdocuments.in/reader035/viewer/2022081514/56649d545503460f94a318b4/html5/thumbnails/14.jpg)
Catabolic pathways for alanine, glycine, serine, cysteine,
tryptophan, and threonine
![Page 15: Entry of Aspartate into the Urea Cycle This is the second nitrogen-acquiring reaction.](https://reader035.fdocuments.in/reader035/viewer/2022081514/56649d545503460f94a318b4/html5/thumbnails/15.jpg)
![Page 16: Entry of Aspartate into the Urea Cycle This is the second nitrogen-acquiring reaction.](https://reader035.fdocuments.in/reader035/viewer/2022081514/56649d545503460f94a318b4/html5/thumbnails/16.jpg)
![Page 17: Entry of Aspartate into the Urea Cycle This is the second nitrogen-acquiring reaction.](https://reader035.fdocuments.in/reader035/viewer/2022081514/56649d545503460f94a318b4/html5/thumbnails/17.jpg)
Interplay of the pyridoxal phosphate and tetrahydrofolate cofactors in serine and glycine metabolism
![Page 18: Entry of Aspartate into the Urea Cycle This is the second nitrogen-acquiring reaction.](https://reader035.fdocuments.in/reader035/viewer/2022081514/56649d545503460f94a318b4/html5/thumbnails/18.jpg)
![Page 19: Entry of Aspartate into the Urea Cycle This is the second nitrogen-acquiring reaction.](https://reader035.fdocuments.in/reader035/viewer/2022081514/56649d545503460f94a318b4/html5/thumbnails/19.jpg)
![Page 20: Entry of Aspartate into the Urea Cycle This is the second nitrogen-acquiring reaction.](https://reader035.fdocuments.in/reader035/viewer/2022081514/56649d545503460f94a318b4/html5/thumbnails/20.jpg)
Catabolic pathways for tryptophan, lysine, phenylalanine, tyrosine, leucine, and isoleucine.
![Page 21: Entry of Aspartate into the Urea Cycle This is the second nitrogen-acquiring reaction.](https://reader035.fdocuments.in/reader035/viewer/2022081514/56649d545503460f94a318b4/html5/thumbnails/21.jpg)
![Page 22: Entry of Aspartate into the Urea Cycle This is the second nitrogen-acquiring reaction.](https://reader035.fdocuments.in/reader035/viewer/2022081514/56649d545503460f94a318b4/html5/thumbnails/22.jpg)
![Page 23: Entry of Aspartate into the Urea Cycle This is the second nitrogen-acquiring reaction.](https://reader035.fdocuments.in/reader035/viewer/2022081514/56649d545503460f94a318b4/html5/thumbnails/23.jpg)
Tryptophan as precursor
![Page 24: Entry of Aspartate into the Urea Cycle This is the second nitrogen-acquiring reaction.](https://reader035.fdocuments.in/reader035/viewer/2022081514/56649d545503460f94a318b4/html5/thumbnails/24.jpg)
Catabolic pathways for phenylalanine and tyrosine. In humans these amino acids are normally converted to acetoacetyl-CoA and fumarate. Genetic defects in many of
these enzymes cause inheritable human diseases.
![Page 25: Entry of Aspartate into the Urea Cycle This is the second nitrogen-acquiring reaction.](https://reader035.fdocuments.in/reader035/viewer/2022081514/56649d545503460f94a318b4/html5/thumbnails/25.jpg)
Role of tetrahydrobiopterin in the phenylalanine hydroxylase reaction. The H atom shaded pink is transferred directly from C-4 to C-3 in the reaction. This feature,
discovered at the National Institutes of Health, is called the NIH shift.
![Page 26: Entry of Aspartate into the Urea Cycle This is the second nitrogen-acquiring reaction.](https://reader035.fdocuments.in/reader035/viewer/2022081514/56649d545503460f94a318b4/html5/thumbnails/26.jpg)
In PKU, phenylpyruvate accumulates in the
tissues, blood, and urine. The urine may also
contain phenylacetate and phenyllactate.
![Page 27: Entry of Aspartate into the Urea Cycle This is the second nitrogen-acquiring reaction.](https://reader035.fdocuments.in/reader035/viewer/2022081514/56649d545503460f94a318b4/html5/thumbnails/27.jpg)
Catabolic pathways for arginine, histidine, glutamate, glutamine, and proline
![Page 28: Entry of Aspartate into the Urea Cycle This is the second nitrogen-acquiring reaction.](https://reader035.fdocuments.in/reader035/viewer/2022081514/56649d545503460f94a318b4/html5/thumbnails/28.jpg)
Catabolic pathways for methionine,
isoleucine, threonine, and valine.
![Page 29: Entry of Aspartate into the Urea Cycle This is the second nitrogen-acquiring reaction.](https://reader035.fdocuments.in/reader035/viewer/2022081514/56649d545503460f94a318b4/html5/thumbnails/29.jpg)
Catabolic pathways for the three branchedchain amino acids: valine, isoleucine, and leucine. All three pathways occur in extrahepatic tissues and share the first two enzymes, as
shown here. The branched-chain α-keto acid dehydrogenase complex is analogous to the pyruvate and α-ketoglutarate dehydrogenase complexes.This enzyme is defective in people with
maple syrup urine disease.
![Page 30: Entry of Aspartate into the Urea Cycle This is the second nitrogen-acquiring reaction.](https://reader035.fdocuments.in/reader035/viewer/2022081514/56649d545503460f94a318b4/html5/thumbnails/30.jpg)
Catabolic pathway for asparagine and aspartate
![Page 31: Entry of Aspartate into the Urea Cycle This is the second nitrogen-acquiring reaction.](https://reader035.fdocuments.in/reader035/viewer/2022081514/56649d545503460f94a318b4/html5/thumbnails/31.jpg)
Chapter 18: Summary
• Amino acids from protein are an important energy source
in carnivorous animals
• Catabolism of amino acids involves transfer of the amino
group via PLP-dependent aminotransferase to a donor
such as -ketoglutarate to yield L-glutamine
• L-glutamine can be used to synthesize new amino acids,
or it can dispose of excess nitrogen as ammonia
• In most mammals, toxic ammonia is quickly recaptured
into carbamoyl phosphate and passed into the urea cycle
In this chapter, we learned that: