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In enzymology, a trypanothione synthase () is an enzyme that catalyzes the chemical reaction :glutathione + glutathionylspermidine + ATP N1,N8-bis(glutathionyl)spermidine + ADP + phosphate The 3 substrates of this enzyme are glutathione, glutathionylspermidine, and ATP, whereas its 3 products are N1,N8-bis(glutathionyl)spermidine, ADP, and phosphate.〔 This reaction is especially important for protozoa in the order kinetoplastida as the molecule of N1,N8-bis(glutathionyl)spermidine, also known as trypanothione, is homologous to the function of glutathione in most other prokaryotic and eukaryotic cells. This means that it is a key intermediate in maintaining thiol redox within the cell and defending against harmful oxidative effects in such protozoa.〔 This enzyme belongs to the family of ligases, specifically those forming carbon-nitrogen bonds as acid-D-ammonia (or amine) ligases (amide synthases). The systematic name of this enzyme class is glutathionylspermidine:glutathione ligase (ADP-forming). == Structure == The active bifunctional enzyme of trypanothione synthase is found as a 74.4 KDa monomer consisting of 652 residues with two catalytic domains.〔〔 Its C-terminal domain is a synthetase and has an ATP-grasp family fold that is usually found in carbon-nitrogen ligases. The N-terminal domain is a cysteine, histidine-dependent aminohydrolase amidase. Structurally the synthetase and amidase domains are bound together by three residues of Glu-650-Asp-651-Glu-652 through hydrogen bonding and salt bridge interactions with basic side chains in order for the protein to properly fold. These three residues also block the catalytic Cys-59 in the amidase domain.〔 It is currently known that the synthetase active site is shaped in the fashion of a triangular cavity that binds the three substrates such that the end of each molecule is nestled in a vertex of the triangle.〔 The particular residues of Arg-553 and Arg-613 have been found to key for synthetic function, however further research into the structure of trypanothione synthase must be done in order to fully understand the enzyme's active sites.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Trypanothione synthase」の詳細全文を読む スポンサード リンク
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