Editing Pyridoxal phosphate (section)

==Non-classical examples of PLP==
PLP is also found on [[glycogen phosphorylase]] in the liver, where it is used to break down [[glycogen]] in [[glycogenolysis]] when [[glucagon]] or [[epinephrine]] signals it to do so. However, this enzyme does not exploit the reactive aldehyde group, but instead utilizes the phosphate group on PLP to perform its reaction.

Although the vast majority of PLP-dependent enzymes form an internal aldimine with PLP via an active site lysine residue, some PLP-dependent enzymes do not have this lysine residue, but instead have a histidine in the active site. In such a case, the histidine cannot form the internal aldimine, and, therefore, the co-factor does not become covalently tethered to the enzyme. [[ColD|GDP-4-keto-6-deoxymannose-3-dehydratase (ColD)]] is an example of such an enzyme.<ref name="pmid16943443">{{cite journal | vauthors = Cook PD, Thoden JB, Holden HM | title = The structure of GDP-4-keto-6-deoxy-D-mannose-3-dehydratase: a unique coenzyme B6-dependent enzyme | journal = Protein Science | volume = 15 | issue = 9 | pages = 2093–106 | date = September 2006 | pmid = 16943443 | pmc = 2242600 | doi = 10.1110/ps.062328306 }}</ref>
Human [[Serine hydroxymethyltransferase]] 2 regulates one-carbon transfer reactions required for amino acid and nucleotide metabolism, and exists in dimeric and tetrameric forms. The dimeric SHMT2 variant is a potent inhibitor of the BRISC deubiquitylase enzyme complex, which regulates immune-based cell signaling. Recent studies show that SJMT2 tetramerization is induced by PLP. This prevents interaction with the BRISC deubiqutylase complex, potentially linking vitamin B6 levels and metabolism to inflammation.<ref>{{cite journal|vauthors=Eyers PA, Murphy JM|date=November 2016|title=The evolving world of pseudoenzymes: proteins, prejudice and zombies|journal=BMC Biology|volume=14|issue=1|pages=98|doi=10.1186/s12915-016-0322-x|pmc=5106787|pmid=27835992 |doi-access=free }}</ref>