Phosphatidylserine decarboxylase

PS is decarboxylated by PS decarboxylase to yield the zwitterionic PE. This inner membrane enzyme has a subunit molecular mass of 36 kDa. PS decarboxylase has a pyruvate prosthetic group that participates in the reaction by forming a Schiff base with PS. Overproduction of the enzyme 30-50-fold by plasmid-bome copies of the psd gene has no effect on membrane phospholipid composition, indicating that the level of this enzyme does not regulate the amount of PE in the membrane. The majority of the PE is found in the periplasmic leaflet of the inner membrane, and there is a rapid flipping from the inner to outer leaflet by the MsbA lipid flippase (Section 7). 

Mutants with a temperature-sensitive decarboxylase accumulate PS at the non-permissive temperature. The mutants continue to grow for several hours after the shift to the non-permissive temperature despite the reduced levels of PE and the concomitant increase in PS. Complete inactivation of psd by insertional mutagenesis has the same divalent cation-requiring phenotype as the pss mutants described above. The requirement for Ptd2Gro is consistent with the inability to introduce a null els allele into psd strains. Thus, PE is essential for the polymorphic regulation of lipid structure. 

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Today s mitochondria lack most of the genes involved in phosphohpid metabolism. Therefore, mitochondria have to import most of their hpids. Phospholipids such as phosphatidylcholine, phosphatidylserine, phosphatidylglycerol, and phosphatidylinositol must be synthesized in the endoplasmatic reticulum under the control of nuclear genes and then transferred to mitochondria (Voelker, 2000) (Figure 1). Mitochondria use both nuclear and mitochondrial encoded proteins to further diversify phospholipids (Dowhan, 1997 Kent, 1995 Daum, 1985). Thus, a nuclear phosphatidylserine decarboxylase converts phosphatidylserine into phosphatidylethanolamine, or mitochondrial encoded cardiolipin synthase converts phosphatidylglycerol into cardiolipin which is incorporated exclusively into the inner mitochondrial membrane. 

Figure 1. Synthetic pathway for PS and PE in mammalian cells. The major steps occuring in the synthesis and interconversion of PS and PE are shown. The PS synthases condense serine with a phosphatidyl moiety derived from PC and PE. The nascent PS can be converted to PE by decarboxylation. PE can also be formed by transfer of a phosphoethanolamine moiety from CDP-ethanolamine to diacylglycerol via the Kennedy pathway. The abbreviations used are PC, phosphatidylcholine PS, phosphatidylserine PE, phosphatidylethanolamine DG, diacylglycerol PSD, phosphatidylserine decarboxylase PSS, PS synthase.

Igarashi, K., Kaneda, M., Yamaji, A., Saido, T.C., Kikkawa, U., Qno, Y., Inoue, K., and Umeda, M., 1995, A novel phosphatidylserine-binding peptide motif defined by an anti-idiotypic monoclonal antibody. Localization of phosphatidylserine-specific binding sites on protein kinase C and phosphatidylserine decarboxylase. J. Biol. Chem. 270 29075-29078. 

Voelker, D.R., 1997, Phosphatidylserine decarboxylase. Biochim. Biophys. Acta. 1348 236-244. 

PHOSPHATIDYLSERINE SYNTHASE PHOSPHATIDYLSERINE DECARBOXYLASE PHOSPHATIDYLSERINE SYNTHASE Phosphinate inhibitor,... 

KYNURENINE AMINOTRANSFERASE LEUCINE AMINOTRANSFERASE LYSINE 2,3-AMINOMUTASE LYSINE 6-AMINOTRANSFERASE LYSINE DECARBOXYLASE METHIONINE y-LYASE ORNITHINE AMINOTRANSFERASE PHENYLALANINE DECARBOXYLASE PHOSPHATIDYLSERINE DECARBOXYLASE... 

Phosphatidylserine and phosphatidylglycerol can serve as precursors of other membrane lipids in bacteria (Fig. 21-25). Decarboxylation of the serine moiety in phosphatidylserine, catalyzed by phosphatidylserine decarboxylase, yields phosphatidylethanolamine. In E. coli, condensation of two molecules of phosphatidylglycerol, with elimination of one glycerol, yields... 

Yeast, like bacteria, can produce phosphatidylserine by condensation of CDP-diacylglycerol and serine, and can synthesize phosphatidylethanolamine from phosphatidylserine in the reaction catalyzed by phosphatidylserine decarboxylase (Fig. 21-27). In mammalian ceils, an alternative route to phosphatidylserine is a head-group... 

Phosphatidylinositol (Ptdlns) 563, 565, 566s in signalling 563 - 566 Phosphatidylinositol 3-kinase 565 Phosphatidylinositol 4,5-bisphosphate 563 Phosphatidylserine 383s, 564 decarboxylation of 753 Phosphatidylserine decarboxylase 409, 755 3 -Phosphoadenosine 5 -phosphosulfate (PAPS) 659 Phosphoadenylation... 

Would you expect phosphatidylserine decarboxylase (fig. 19.3) to be a pyridoxal phosphate enzyme ... 

Griac, P., 1997, Regulation of yeast phospholipid biosynthetic genes in phosphatidylserine decarboxylase mutants. J. Bacteriol. 179 5843-5848. 

Other pyruvate-containing enzymes include aspartate -decarboxylase from Escherichia coli, the enzyme that catalyzes the formation of -alanine for the synthesis of pantothenic acid (Section 12.2.4) proline reductase from Clostridium sticklandiv, phosphatidylserine decarboxylase from E. coli and phenylalanine aminotransferase from Pseudomonas fluorescens. Phospho-pantetheinoyl cysteine decarboxylase, involved in the synthesis of coenzyme A (Section 12.2.1), and S-adenosylmethionine decarboxylase seem to be the only mammalian pyruvoyl enzymes (Snell, 1990). 

Many of the proteins of membranes are enzymes. For example, the entire electron transport system of mitochondria (Chapter 18) is embedded in membranes and a number of highly lipid-soluble enzymes have been isolated. Examples are phosphatidylserine decarboxylase, which converts phosphatidylserine to phosphatidylethanolamine in biosynthesis of the latter, and isoprenoid alcohol phosphokinase, which participates in bacterial cell wall synthesis (Chapter 20). A number of ectoenz5rmes are present predominantly on the outsides of cell membranes. Enzymes such as phospholipases (Chapter 12), which are present on membrane surfaces, often are relatively inactive when removed from the lipid environment but are active in the presence of phospholipid bilay-gj-g 330,331 jp,g distribution of lipid chain lengths as well as the cholesterol content of the membrane can affect enzymatic activities. ... 

Baunaure, F., Eldin, P., Cathiard, A. M., and Vial, H. (2004). Characterization of a non-mitochondrial type I phosphatidylserine decarboxylase in Plasmodium falciparum. Mol. 

Pyruvoyl cofactor is derived from the posttranslational modification of an internal amino acid residue, and it does not equilibrate with exogenous pyruvate. Enzymes that possess this cofactor play an important role in the metabolism of biologically important amines from bacterial and eukaryotic sources. These enzymes include aspartate decarboxylase, arginine decarboxylase," phosphatidylserine decarboxylase, . S-adenosylmethionine decarboxylase, histidine decarboxylase, glycine reductase, and proline reductase. ... 

Fig. 6. Synthesis of phospholipid polar head groups. The three major phospholipid species in E. coli are synthesized by a total of six different enzymatic activities (1) phosphatidate cytidylyltransferase (Cds), (2) phosphatidylserine synthase (PssA), (3) phosphatidylserine decarboxylase (Psd), (4) phosphatidyl-glycerol phosphate synthase (PgsA), (5) phosphatidylglycerol phosphate phosphatase (PgpA or PgpB), and (6) cardiolipin synthase (els).

Mouse Pisd Phosphatidylserine decarboxylase Embryonic lethal -day 8... 

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