Catalytic domain of phospholipase D superfamily proteins; Catalytic domain of phospholipase D (PLD) superfamily proteins. The PLD superfamily is composed of a large and diverse group of proteins including plant, mammalian and bacterial PLDs, bacterial cardiolipin (CL) synthases, bacterial phosphatidylserine synthases (PSS), eukaryotic phosphatidylglycerophosphate (PGP) synthase, eukaryotic tyrosyl-DNA phosphodiesterase 1 (Tdp1), and some bacterial endonucleases (Nuc and BfiI), among others. PLD enzymes hydrolyze phospholipid phosphodiester bonds to yield phosphatidic acid and a free polar head group. They can also catalyze the transphosphatidylation of phospholipids to acceptor alcohols. The majority of members in this superfamily contain a short conserved sequence motif (H-x-K-x(4)-D, where x represents any amino acid residue), called the HKD signature motif. There are varying expanded forms of this motif in different family members. Some members contain variant HKD motifs. Most PLD enzymes are monomeric proteins with two HKD motif-containing domains. Two HKD motifs from two domains form a single active site. Some PLD enzymes have only one copy of the HKD motif per subunit but form a functionally active dimer, which has a single active site at the dimer interface containing the two HKD motifs from both subunits. Different PLD enzymes may have evolved through domain fusion of a common catalytic core with separate substrate recognition domains. Despite their various catalytic functions and a very broad range of substrate specificities, the diverse group of PLD enzymes can bind to a phosphodiester moiety. Most of them are active as bi-lobed monomers or dimers, and may possess similar core structures for catalytic activity. They are generally thought to utilize a common two-step ping-pong catalytic mechanism, involving an enzyme-substrate intermediate, to cleave phosphodiester bonds. The two histidine residues from the two HKD motifs play key roles in the catalysis. Upon substrate binding, a histidine from one HKD motif could function as the nucleophile, attacking the phosphodiester bond to create a covalent phosphohistidine intermediate, while the other histidine residue from the second HKD motif could serve as a general acid, stabilizing the leaving group.

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gi 193208606  76 VCESIPAGMTFNSSYpIFNSTTDCWMRLMSEAKEEILIGSYYWSLLVKDTGDGYTTD 132
Cdd:cd09106    1 LVESIPEGLTFLSSS-SHLSTFEAWMELISSAKKSIDIASFYWNLRGTDTNPDSSAQ 56

Putative catalytic domain, repeat 1, of vertebrate phospholipases, PLD3, PLD4 and PLD5, viral envelope proteins K4 and p37, and similar proteins; Putative catalytic domain, repeat 1, of vertebrate phospholipases D, PLD3, PLD4, and PLD5 (EC 3.1.4.4), viral envelope proteins (vaccinia virus proteins K4 and p37), and similar proteins. Most family members contain two copies of the HKD motifs (H-x-K-x(4)-D, where x represents any amino acid residue), and have been classified into the phospholipase D (PLD) superfamily. Proteins in this subfamily are associated with Golgi membranes, altering their lipid content by the conversion of phospholipids into phosphatidic acid, which is thought to be involved in the regulation of lipid movement. ADP ribosylation factor (ARF), a small guanosine triphosphate binding protein, might be required activity. The vaccinia virus p37 protein, encoded by the F13L gene, is also associated with Golgi membranes and is required for the envelopment and spread of the extracellular enveloped virus (EEV). The vaccinia virus protein K4, encoded by the HindIII K4L gene, remains to be characterized. Sequence analysis indicates that the vaccinia virus proteins K4 and p37 might have evolved from one or more captured eukaryotic genes involved in cellular lipid metabolism. Up to date, no catalytic activity of PLD3 has been shown. Furthermore, due to the lack of functional important histidine and lysine residues in the HKD motif, mammalian PLD5 has been characterized as an inactive PLD. The poxvirus p37 proteins may also lack PLD enzymatic activity, since they contain only one partially conserved HKD motif (N-x-K-x(4)-D).

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gi 193208606  76 VCESIPAGMTFNSSYpIFNSTTDCWMRLMSEAKEEILIGSYYWSLLVKDTGDGYTTD 132
Cdd:cd09106    1 LVESIPEGLTFLSSS-SHLSTFEAWMELISSAKKSIDIASFYWNLRGTDTNPDSSAQ 56

Putative catalytic domain, repeat 1, of vertebrate phospholipases, PLD3, PLD4 and PLD5, viral envelope proteins K4 and p37, and similar proteins; Putative catalytic domain, repeat 1, of vertebrate phospholipases D, PLD3, PLD4, and PLD5 (EC 3.1.4.4), viral envelope proteins (vaccinia virus proteins K4 and p37), and similar proteins. Most family members contain two copies of the HKD motifs (H-x-K-x(4)-D, where x represents any amino acid residue), and have been classified into the phospholipase D (PLD) superfamily. Proteins in this subfamily are associated with Golgi membranes, altering their lipid content by the conversion of phospholipids into phosphatidic acid, which is thought to be involved in the regulation of lipid movement. ADP ribosylation factor (ARF), a small guanosine triphosphate binding protein, might be required activity. The vaccinia virus p37 protein, encoded by the F13L gene, is also associated with Golgi membranes and is required for the envelopment and spread of the extracellular enveloped virus (EEV). The vaccinia virus protein K4, encoded by the HindIII K4L gene, remains to be characterized. Sequence analysis indicates that the vaccinia virus proteins K4 and p37 might have evolved from one or more captured eukaryotic genes involved in cellular lipid metabolism. Up to date, no catalytic activity of PLD3 has been shown. Furthermore, due to the lack of functional important histidine and lysine residues in the HKD motif, mammalian PLD5 has been characterized as an inactive PLD. The poxvirus p37 proteins may also lack PLD enzymatic activity, since they contain only one partially conserved HKD motif (N-x-K-x(4)-D).

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gi 193208606  76 VCESIPAGMTFNSSYpIFNSTTDCWMRLMSEAKEEILIGSYYWSLLVKDTGDGYTTD 132
Cdd:cd09106    1 LVESIPEGLTFLSSS-SHLSTFEAWMELISSAKKSIDIASFYWNLRGTDTNPDSSAQ 56

Putative catalytic domain, repeat 1, of vertebrate phospholipase PLD4; Putative catalytic domain, repeat 1, of vertebrate phospholipases D4 (PLD4, EC 3.1.4.4), homologs of the vaccinia virus protein K4 which is encoded by the HindIII K4L gene. Due to the presence of two copies of the conserved HKD motif (H-x-K-x(4)-D, where x represents any amino acid residue), PLD4 has been assigned to PLD superfamily although no catalytic activity has been detected to date. Unlike PLD1 and PLD2, PLD4 does not contain Phox (PX) and Pleckstrin homology (PH) domains but has a putative transmembrane domain. Like other vertebrate homologs of protein K4, PLD4 might be associated with Golgi membranes and alter their lipid content by selectively hydrolyze phosphatidylcholine (PC) into corresponding phosphatidic acid, which is thought to be involved in the regulation of lipid movement.

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gi 193208606  78 ESIPAGMTFNSSYPIFNSTTDCWMRLMSEAKEEILIGSYYWSLLVKDTGDGYTTD 132
Cdd:cd09145    3 ESIPEDLTYEGNSTFALPLQKAWTKLLDMAQEQVHVASYYWSLTGEDIGVNDSSS 57