Editing Adenosine triphosphate (section)

==ATP analogues==
Biochemistry laboratories often use ''[[in vitro]]'' studies to explore ATP-dependent molecular processes. ATP analogs are also used in [[X-ray crystallography]] to determine a [[protein structure]] in complex with ATP, often together with other substrates.{{citation needed|date=April 2023}}

[[Enzyme inhibitor]]s of ATP-dependent enzymes such as [[kinase]]s are needed to examine the [[binding site]]s and [[transition state]]s involved in ATP-dependent reactions.{{citation needed|date=April 2023}}

Most useful ATP analogs cannot be hydrolyzed as ATP would be; instead, they trap the enzyme in a structure closely related to the ATP-bound state. Adenosine 5′-(γ-thiotriphosphate) is an extremely common ATP analog in which one of the gamma-phosphate oxygens is replaced by a [[sulfur]] atom; this anion is hydrolyzed at a dramatically slower rate than ATP itself and functions as an inhibitor of ATP-dependent processes. In crystallographic studies, hydrolysis transition states are modeled by the bound [[vanadate]] ion.

Caution is warranted in interpreting the results of experiments using ATP analogs, since some enzymes can hydrolyze them at appreciable rates at high concentration.<ref name=Resetar>{{cite journal |last1=Resetar |first1=A.&nbsp;M. |last2=Chalovich |first2=J.&nbsp;M. | year=1995 | title= Adenosine 5′-(gamma-thiotriphosphate): an ATP analog that should be used with caution in muscle contraction studies | volume=34 | issue=49 | pages=16039–16045 | pmid=8519760 | doi = 10.1021/bi00049a018 | journal= Biochemistry}}</ref>