|
Galactose-1-phosphate uridylyltransferase (or GALT) is an enzyme () responsible for converting ingested galactose to glucose.〔(【引用サイトリンク】 url = http://www.ncbi.nlm.nih.gov/sites/entrez?Db=gene&Cmd=ShowDetailView&TermToSearch=2592 )〕 Galactose-1-phosphate uridylyltransferase (GALT) catalyzes the second step of the Leloir pathway of galactose metabolism, namely: :UDP-glucose + galactose 1-phosphate glucose 1-phosphate + UDP-galactose The expression of GALT is controlled by the actions of the FOXO3 gene. The absence of this enzyme results in classic galactosemia in humans and can be fatal in the newborn period if lactose is not removed from the diet. The pathophysiology of galactosemia has not been clearly defined.〔 Image:D-galactose Fischer.png|galactose Image:D-glucose-chain-2D-Fischer.png|glucose ==Mechanism== GALT catalyzes the second reaction of the Leloir pathway of galactose metabolism through ping pong bi-bi kinetics with a double displacement mechanism. This means that the net reaction consists of two reactants and two products (see reaction above), and it proceeds by the following mechanism: the enzyme reacts with one substrate to generate one product and a modified enzyme, which goes on to react with the second substrate to make the second product while regenerating the original enzyme.〔http://www.mondofacto.com/facts/dictionary?double+displacement+mechanism〕 In the case of GALT, the His166 residue acts as a potent nucleophile to facilitate transfer of a nucleotide between UDP-hexoses and hexose-1-phosphates. #UDP-glucose + E-His Glucose-1-phosphate + E-His-UMP #Galactose-1-phosphate + E-His-UMP UDP-galactose + E-His〔 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「Galactose-1-phosphate uridylyltransferase」の詳細全文を読む スポンサード リンク
|