Publications

• Cloning and expression of murine liver phosphatidylserine synthase (PSS)-2: differential regulation of phospholipid metabolism by PSS1 and PSS2.

  Stone S.J., Vance J.E.

  Phosphatidylserine (PtdSer) is synthesized in mammalian cells by two base-exchange enzymes: PtdSer synthase (PSS)-1 primarily uses phosphatidylcholine as a substrate for exchange with serine, whereas PSS2 uses phosphatidylethanolamine (PtdEtn). We previously expressed murine PSS1 in McArdle hepato ... >> More

  Phosphatidylserine (PtdSer) is synthesized in mammalian cells by two base-exchange enzymes: PtdSer synthase (PSS)-1 primarily uses phosphatidylcholine as a substrate for exchange with serine, whereas PSS2 uses phosphatidylethanolamine (PtdEtn). We previously expressed murine PSS1 in McArdle hepatoma cells. The activity of PSS1 in vitro and the synthesis of PtdSer and PtdSer-derived PtdEtn were increased, whereas PtdEtn synthesis from the CDP-ethanolamine pathway was inhibited [Stone, Cui and Vance (1998) J. Biol. Chem. 273, 7293-7302]. We have now cloned and stably expressed a murine PSS2 cDNA in McArdle cells and M.9.1.1 cells [which are ethanolamine-requiring mutant Chinese hamster ovary (CHO) cells defective in PSS1]. Expression of the PSS2 in M.9.1.1 cells reversed the ethanolamine auxotrophy. However, the PtdEtn content was not normalized unless the culture medium was supplemented with ethanolamine. In both M.9.1.1 and hepatoma cells transfected with PSS2 cDNA the rate of synthesis of PtdSer and PtdSer-derived PtdEtn did not exceed that in parental CHO cells or control McArdle cells respectively, in contrast to cells expressing similar levels of murine PSS1. These observations suggest that PtdSer synthesis via murine PSS2, but not PSS1, is regulated by end-product inhibition. Moreover, expression of murine PSS2 in McArdle cells did not inhibit PtdEtn synthesis via the CDP-ethanolamine pathway, whereas expression of similar levels of PSS1 activity inhibited this pathway by approx. 50%. We conclude that murine PSS1 and PSS2, which are apparently derived from different genes, independently modulate phospholipid metabolism. In addition, mRNAs encoding the two synthases are differentially expressed in several murine tissues, supporting the idea that PSS1 and PSS2 might perform unique functions. << Less

  Biochem. J. 342:57-64(1999) [PubMed] [EuropePMC]

• Phosphatidylserine synthase 2: high efficiency for synthesizing phosphatidylserine containing docosahexaenoic acid.

  Kimura A.K., Kim H.Y.

  Phosphatidylserine (PS), the major anionic phospholipid in eukaryotic cell membranes, is synthesized by the integral membrane enzymes PS synthase 1 (PSS1) and 2 (PSS2). PSS2 is highly expressed in specific tissues, such as brain and testis, where docosahexaenoic acid (DHA, 22:6n-3) is also highly ... >> More

  Phosphatidylserine (PS), the major anionic phospholipid in eukaryotic cell membranes, is synthesized by the integral membrane enzymes PS synthase 1 (PSS1) and 2 (PSS2). PSS2 is highly expressed in specific tissues, such as brain and testis, where docosahexaenoic acid (DHA, 22:6n-3) is also highly enriched. The purpose of this work was to characterize the hydrocarbon-chain preference of PSS2 to gain insight on the specialized role of PSS2 in PS accumulation in the DHA-abundant tissues. Flag-tagged PSS2 was expressed in HEK cells and immunopurified in a functionally active form. Purified PSS2 utilized both PE plasmalogen and diacyl PE as substrates. Nevertheless, the latter was six times better utilized, indicating the importance of an ester linkage at the sn-1 position. Although no sn-1 fatty acyl preference was noted, PSS2 exhibited significant preference toward DHA compared with 18:1 or 20:4 at the sn-2 position. Preferential production of DHA-containing PS (DHA-PS) was consistently observed with PSS2 purified from a variety of cell lines as well as with microsomes from mutant cells in which PS synthesis relies primarily on PSS2. These findings suggest that PSS2 may play a key role in PS accumulation in brain and testis through high activity toward DHA-containing substrates that are abundant in these tissues. << Less

  J. Lipid Res. 54:214-222(2013) [PubMed] [EuropePMC]

  This publication is cited by 9 other entries.

• Purification and characterization of human phosphatidylserine synthases 1 and 2.

  Tomohiro S., Kawaguti A., Kawabe Y., Kitada S., Kuge O.

  PS (phosphatidylserine) in mammalian cells is synthesized by two distinct base-exchange enzymes, PSS1 (PS synthase 1) and PSS2, which are responsible for the conversion of PC (phosphatidylcholine) and PE (phosphatidylethanolamine) respectively into PS in intact cells. The PS synthesis in cultured ... >> More

  PS (phosphatidylserine) in mammalian cells is synthesized by two distinct base-exchange enzymes, PSS1 (PS synthase 1) and PSS2, which are responsible for the conversion of PC (phosphatidylcholine) and PE (phosphatidylethanolamine) respectively into PS in intact cells. The PS synthesis in cultured mammalian cells is inhibited by exogenous PS, and this feedback control occurs through inhibition of PSSs by PS. In the present study, we purified epitope-tagged forms of human PSS1 and PSS2. The purified PSS2 was shown to catalyse the conversion of PE, but not PC, into PS, this being consistent with the substrate specificity observed in intact cells. On the other hand, the purified PSS1 was shown to catalyse the conversion of both PC and PE into PS, although PSS1 in intact cells had been shown not to contribute to the conversion of PE into PS to a significant extent. Furthermore, we found that the purified PSS2, but not the purified PSS1, was inhibited on the addition of PS to the enzyme assay mixture, raising the possibility that there was some difference between the mechanisms of the inhibitory actions of PS towards PSS1 and PSS2. << Less

  Biochem. J. 418:421-429(2009) [PubMed] [EuropePMC]

  This publication is cited by 1 other entry.