Editing Vesicular monoamine transporter (section)

==Kinetics==
VMATs have a relatively low [[Michaelis–Menten kinetics|V<sub>max</sub>]], with an estimated rate of 5–20/sec depending on the substrate.<ref>{{cite journal | author = Peter D | year = 1994 | title = The chromaffin granule and synaptic vesicle amine transporters differ in substrate recognition and sensitivity to inhibitors | journal = J Biol Chem | volume = 269 | issue = 10 | pages = 7231–7237 | doi = 10.1016/S0021-9258(17)37272-1 | pmid = 8125935 |display-authors=etal| doi-access = free }}</ref> Vesicle filling may limit monoamine release from neurons with high rates of firing.

Specific amine-binding affinity varies by VMAT isoform; studies indicate that [[catecholamine]]s dopamine, norepinephrine, and epinephrine have a threefold higher affinity for VMAT2 than VMAT1 binding and uptake.<ref name="Wimalasena, K. 2011"/><ref name="Chaudhry FA 2007"/><ref name="Erickson JD 1996">{{cite journal |vauthors=Erickson JD, Schafer MK, Bonner TI, Eiden LE, Weihe E | year = 1996 | title = Distinct pharmacological properties and distribution in neurons and endocrine cells of two isoforms of the human vesicular monoamine transporter | journal = Proc. Natl. Acad. Sci. USA | volume = 93 | issue = 10| pages = 5166–5171 | doi=10.1073/pnas.93.10.5166 | pmid=8643547 | pmc=39426| bibcode = 1996PNAS...93.5166E | doi-access = free }}</ref> The imidazoleamine histamine has a thirtyfold higher affinity for VMAT2 compared to VMAT1,<ref name="Wimalasena, K. 2011"/> and is thought to bind to a different site than other monoamines.<ref name="Chaudhry FA 2007"/> Unlike catecholamines and histamine, the [[indoleamine]] serotonin binds to VMAT1 and VMAT2 with a similar affinity for both transporter isoforms.<ref name="Wimalasena, K. 2011"/><ref name="Erickson JD 1996"/>

VMAT1 has a lower turnover number and a lower affinity for most monoamine substrates than VMAT2, which may be because of VMAT2's location in the central nervous system, which demands fast recovery from neurotransmitter release in order to prepare for subsequent releases. The uptake efficiencies of each VMAT substrate can be ranked in order of efficiency as: serotonin, dopamine, epinephrine, and norepinephrine.<ref name="Wimalasena, K. 2011"/>

[[Methamphetamine|Methamphetamines]] decrease V<sub>max</sub>, while [[cocaine]] increases V<sub>max</sub> reversibly in rat brain.<ref name="Wimalasena, K. 2011"/>