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The PDE2 (phosphodiesterase 2) enzyme is one of 21 different phosphodiesterases (PDE) found in mammals. These different PDEs can be subdivided to 11 families (PDE1 – PDE11). The different PDEs of the same family are functionally related despite the fact that their amino acid sequences show considerable divergence. The PDEs have different substrate specificities. Some are cAMP (''figure 1'') selective hydrolases (PDE 4, -7 and -8), others are cGMP (''figure 1'') selective hydrolases (PDE 5, -6 and -9) and the rest can hydrolyse both cAMP and cGMP (PDE1, -2, -3, -10 and -11). There is only one gene family coding for the PDE2, which is the PDE2A. Three splice variants have been found, the PDE2A1, PDE2A2 and PDE2A3 (PDE2A2 has only been found in rats). PDE2A1 is cytosolic whereas -A2 and -A3 are membrane bound. It has been suggested that different localization of PDE2A2 and -A3 is due to a unique N-terminal sequence, which is absent in PDE2A1. Despite the PDE2A splice variants being different, there is no known differences in their kinetic behavior. (See review article ). == Crystal structure == The crystal structure of the active site of the PDE2 enzyme has been reported. (Picture online: ). Even though amino acid sequences, for members of the PDE family show considerable difference (25-35% identity), the overall folding, functional and structural elements of the active sites are very similar. The active site is formed by residues that are highly conserved among all PDEs. The binding pocket contains metal ion (zinc and magnesium) binding sites. The two histidine and two aspartic acid residues, which bind zinc are conserved among all studied PDEs (See review article 〔). The structure of several other PDE iso-enzymes has been elucidated and among them few co-crystal structures, with inhibitors residing in the active site. The co-crystal structures for PDE4B, PDE4D and PDE5A have revealed two common features of inhibitor binding to PDEs. One is a planar ring structure of the inhibitors, which align in the active site of the enzymes and the other is a conserved glutamine residue (the “glutamine switch” mentioned below), which is essential for nucleotide recognition and selectivity.〔〔 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「Phosphodiesterase 2」の詳細全文を読む スポンサード リンク
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