Serine dehydratase

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Serine dehydratase
Chr. 12 q24.21
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Serine dehydratase or

pyruvate, with the release of ammonia.[1]

This enzyme has one

pyruvate and NH3, and uses one cofactor, pyridoxal phosphate (PLP). The enzyme's main role is in gluconeogenesis in the liver's cytoplasm.[citation needed
]

Nomenclature

Serine Dehydratase is also known as:[2]

  • L-serine ammonia-lyase
  • Serine deaminase
  • L-hydroxyaminoacid dehydratase
  • L-serine deaminase
  • L-serine dehydratase
  • L-serine hydro-lyase

Structure

The

catalytic domain that binds PLP and a small domain. The domains are linked by two residues 32-35 and 138-146, with the internal gap created being the space for the active site[1]

Cofactor Binding

The

phosphate group of PLP is coordinated by main chain amides from the tetraglycine loop.[1][3]
(Figure 3 and Figure 4).

Mechanism

The

pyruvate.[4]

Inhibitors

According to the series of assays performed by Cleland (1967), the linear rate of

competitively inhibit the enzyme SDH.[5] The reason that SDH activity is inhibited by L-cysteine is because an inorganic sulfur is created from L-Cysteine via Cystine Desulfrase and sulfur-containing groups are known to promote inhibition.[6]
L-threonine competitively inhibits Serine Dehydratase as well.

Moreover, insulin is known to accelerate

pyruvate that can be converted into free glucose. And glucagon
gives the signal to repress gluconeogenesis and increase the amount of free glucose in the blood by releasing glycogen stores from the liver.

Homocysteine, a compound that SDH combines with Serine to create cystathionine, also noncompetitively inhibits the action of SDH. Studies have shown that homocysteine reacts with SDH's PLP coenzyme to create a complex. This complex is devoid of coenzyme activity and SDH is not able to function (See Enzyme Mechanism Section).[10] In general, homocysteine is an amino acid and metabolite of methionine; increased levels of homocysteine can lead to homocystinuria(see section Disease Relevance).[11]

Biological function

In general, SDH levels decrease with increasing mammalian size.[12]

SDH enzyme plays an important role in gluconeogenesis. Activity is augmented by

oxaloacetate, and, thus, glucose.[13]

Little is known about the properties and the function of human SDH because human liver has low SDH activity. In a study done by Yoshida and Kikuchi, routes of glycine breakdown were measured. Glycine can be converted into serine and either become pyruvate via serine dehydratase or undergo

methylene-THF, ammonia, and carbon dioxide. Results showed the secondary importance of the SDH pathway.[13][14]

Disease relevance

SDH may be significant in the development of hyperglycemia and tumors.

carcinomas, and in tumors of human and rodent origin.[15]

Evolution

Human and rat serine dehydratase

threonine dehydratase and human serine dehydratase. Human SDH shows sequence homology of 27% with the yeast enzyme and 27% with the E. coli enzyme.[16] Overall PLP enzymes exhibit high conservation of the active site residues.[16]

External links

References

  1. ^
    PMID 15689518
    .
  2. ^ "KEGG ENZYME Database Entry". Kyoto Encyclopedia of Genes and Genomes. Kanehisa Laboratories. Retrieved 17 May 2011.
  3. PMID 18245280
    .
  4. PMID 14596599
    .
  5. PMID 322657
    .
  6. PMID 5358627
    .
  7. PMID 14264889
    .
  8. PMID 5488777
    .
  9. PMID 1654838
    .
  10. PMID 4398884
    .
  11. S2CID 29790535
    .
  12. PMID 318433
    .
  13. ^
    PMID 6089514
    .
  14. PMID 1671321
    .
  15. PMID 3126791
    .
  16. ^
    PMID 2674117
    .
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