Comparative studies of biosynthesis of galactolipids in Euglena gracilis strain Z.

Abstract

Biosynthesis of galactolipids in spinach chloroplasts has been reported (2,5). In these studies uridine diphosphate galactose was used as a galactosyl donor to some endogenous acceptor (diglyceride) (Branson Instruments Inc.). Chloroplasts were isolated from the broken cells by the procedure described by Carell and Kahn (Flb fraction) (1). The purity of the chloroplasts was checked under a microscope. Enzymatic synthesis of galactolipids was carried out by the method described previously (2). A typical reaction mixture contained, in 1 ml: uridine diphosphate galactose ("C) (0.03 lac giving 24,000 cpm with specific radioactivity of 25 Ac ,Mmole) in 0.1 ml; chloroplasts or broken cells (dark-grown cells) equivalent to about 5 mg of proteins in 0.5 ml; 0.4 ml of 0.1 M tris buffer, pH 7.4. At the end of a 1-hr reaction at 37 C, the reaction was stopped by adding 4 ml of chloroform-methanol (2:1 v/v) and heating at 55 C for 5 min. The lipid products were extracted once more with 2 ml of the chloroform-methanol solution. The lipid extract was washed four times with 2.5 ml of 0.9%c aqueous sodium chloride solution to remove residual radioactive uridine diphosphate galactose. A 1-ml aliquot of the lipid extract was transferred to a planchet, dried, and counted. The rest of the lipid extract was concentrated and separated on a column packed with silicic acid (Unisil, Clarkson Co., Williamsport, Penn.) into monogalactosyl diglyceride and digalactosyl diglyceride by eluting the column with 100 ml of a solution of 5% diethyl ether in methanol and equal volume of 20% diethyl ether in methanol, respectively. Each eluate was concentrated and counted on a planchet by means of a gas flow counter (Nuclear-Chicago).

Proteome of the secondary plastid of Euglena gracilis reveals metabolic quirks and colourful history

“…This is probably related to the loss of starch synthesis during the emergence of the euglenophyte secondary plastid and the switch to extraplastidial paramylon (-1,3-glucan) as the main storage compound (Barsanti et al 2001 The E. gracilis plastid is also a site for biosynthesis of fatty acids and glycerolipids. The latter include the major plastid phospholipid phosphatidylglycerol and three glycolipids, monogalactosyl-and digalactosyldiacylglycerol (MGDG and DGDG) and sulfoquinovosyl-diacylglycerol (SQDG), in agreement with biochemical evidence documenting these lipids in the E. longa plastid (Matson et al 1970;Blee and Schantz 1978;Shibata et al 2018). We were able to reconstruct pathways for synthesizing these compounds, albeit with several enzymes missing from the proteome, but predicted by the transcriptome.…”

Metabolic quirks and the colourful history of the Euglena gracilis secondary plastid

“…The E. gracilis plastid is also a site for biosynthesis of fatty acids and glycerolipids, the latter including the major plastid phospholipid phosphatidylglycerol and three glycolipids, monogalactosyl‐ and digalactosyl‐diacylglycerol (MGDG and DGDG) and sulfoquinovosyl‐diacylglycerol (SQDG) (Matson & Meifei ; Blee & Schantz, ; Shibata et al ., ). We reconstructed pathways for the synthesis of these compounds, albeit with several enzymes only predicted by the transcriptome.…”

Toxoplasma gondiiacyl-lipid metabolism:de novosynthesis from apicoplast-generated fatty acids versus scavenging of host cell precursors

“…A similar process has been shown to occur in Euglena gracilis whose plastid also finds its origin from a secondary endosymbiosis. The E. gracilis chloroplastic MGDG is so rapidly transformed into DGDG that its synthesis is nearly not detectable [52]. In plants, plastids are also characterized Table 2 Gene candidates for acyl-lipid metabolism in T. gondii EC number: enzyme nomenclature following recommendation of the International Union of Biochemistry and Molecular Biology.…”