Possible role of Yeast and Plant Lysophospholipid: Acyl-CoA Acyltransferases in Remodeling of Phospholipids and Acyl-CoA Pool
Katarzyna Jasieniecka-Gazarkiewicz1, Walentyna Banaś2, Kamil Demski1, 
Antoni Banaś1
1Intercollegiate Faculty of Biotechnology of University of Gdańsk and Medical University of Gdańsk, Kładki 24, 80-822 Gdańsk, Poland 
2Institute of Biology, University of Natural Sciences and Humanities, Siedlce, Poland 

Yeast (BY4742) with disrupted YOR175c gene (encoding the most active yeast LPLAT) were either transformed with pYES2 (empty plasmid) or one of the four different genes encoding enzymes with LPLAT activity: At1g63050, At2g45670 (Arabidopsis LPCAT and LPEAT), YOR175c and SLC1 (yeast LPCAT and LPAAT). Microsomes prepared from transformed yeast cells were used in assays, which demonstrated their ability to remodel PC, PE and PA. Microsomes were incubated with [14C]18:1-CoA in the presence of BSA and CoA. Incubation was performed in two variants: with and without the addition of DTNB. Incorporation of [14C]18:1 into PC, PE and PA in assays without DTNB was treated as a results of the forward (low amount of endogenous LPL can exist in microsomal fractions) and the backward reaction. In assays with DTNB this incorporation was treated only as results of the forward reaction (DTNB binds CoA). The differences between [14C]18:1 incorporated into phospholipids in assays without DTNB and with DTNB were treated only as the result of the backward reaction. 
The backward reactions in assays with microsomal fractions from yeast overexpressed with At1g63050 were most effective towards PC followed by PE and PA. The remodelling of PE and PA started later and was slower than remodeling of PC. In case of microsomal fractions from yeast overexpressed with At2g45670, PE was remodelled most efficiently followed by PC and PA. In assays with microsomes from yeast overexpressed with YOR175c, PC and PE were remodelled. The remodelling of PC was faster than remodelling of PE. The most effective backward reactions in assays with microsomal fraction overexpressed with SLC1, were observed towards PA. 
The above observations were further supported by assays determining the existence of [14C] in acyl-CoA and with assays determining the presence of fatty acid from added acyl-CoAs in studied phospholipids by GC analyses.