Influence of Acyl Chain Composition on the Degradation of Phosphatidylcholine by Phospholipase D in Carnation Microsomal Membranes

Modification of Phospholipid Catabolism in Microsomal Membranes of [gamma]-Irradiated Cauliflower (Brassica oleracea L.)

“…Todd et al (1990) used the same substrate to identify water-soluble breakdown products of PC in tomato fruit. The same group (Brown et al, 1990) showed that unsaturated species of PC were more rapidly degraded than saturated (16:0/16:0)-PC. It is, therefore, more than likely that, had naturally occumng lesssaturated species been used as substrates, the changes observed during senescence and after y irradiation would have been similar, although probably enhanced.…”

“…Phospholipase D was apparently more intimately bound to the membranes than PA phosphatase and lipolytic acyl hydrolase activities because PA accumulated at the expense of the other breakdown products. Partia1 membrane solubilization with Triton X-100 led to enrichment of phospholipase D and PA phosphatase activities in bean membranes, but it also led to reduced PC catabolism in carnation membranes Brown et al, 1990). The absence of OP accumulation in solubilized cauliflower membranes might be interpreted as reduced lipoxygenase activity.…”

“…A 700-mL sample of the chloroform phase was evaporated under nitrogen, dissolved in 20 pL of ch1oroform:methanol (21, v/ v), and spotted on a 250-pm silica gel G plate (Analtech, Newark, DE). Authentic standards (PC, PA, FFA, DG), and ether-extracted FFA peroxides obtained from peroxidation of linoleic acid by soybean lipoxygenase (Brown et al, 1990) were run on parallel lanes. The plates were developed halfway in ch1oroform:acetic acid:methanol:water (70:25:5:2, v/ v; Todd et al, 1990), dried under nitrogen, and fully developed in hexane:diethyl ether:acetic acid (70:30:1, v/v).…”

“…Decreased synthesis of phospholipids, increased phospholipid catabolism, or both have been proposed to be responsible for the process (Suttle and Kende, 1980;Borochov et al, 1982). Phospholipase D, PA phosphatase, and lipolytic acyl hydrolase were associated with microsomal membranes of carnation flowers Brown et al, 1990), bean cotyledons , and tomato fruits (Todd et al, 1990). However, declining microsomal phospholipid content in senescing carnation flowers was not correlated with increased membrane-associated phospholipase activity (Brown et al, 1991).…”

Activation of phospholipase D by calmodulin antagonists and mastoparan in carnation petals

“…PLD could be involved in phospholipid turnover that maintains cell viability and homeostasis (reviewed by Dawidowicz, 1987). Additionally, the observation that the phospholipid content of petals, fruits and leaves decreased during senescence (McArthur et al, 1964;Ferguson and Simon, 1973;Beutelmann and Kende, 1977;Thompson et al, 1982) led to the hypothesis that PLD initiated this lipid breakdown (Brown et al, 1990;Paliyath and Droillard, 1992). The idea was partly based on changes in PLD activity that were measured using in vitro assays (Herman and Chrispeels, 1980;Borochov et al, 1982;Salama and Pearce, 1993), but recently, it was shown that regulation of PLD activity is more complicated.…”