Fat Metabolism in Germinating Soybeans. I. Physiology of Native Fat

Compartmental Utilization of Carboxyl-14C-Tripalmitin by Tissue Homogenate of Pine Seeds

“…Labeled acetyl-CoA and intermediate of p-oxidation were found in both organelle-containing fractions. The supernatant fraction contained radioactive diglycerides, monoglycerides, palmitate, sterol esters, and phospholipids, indicating lipase activity and direct utilization of fatty acid for the synthesis of sterol esters and polar lipids.Germinating fatty seeds hydrolyze reserve triglycerides to fatty acids and glycerol by lipases associated with fat bodies or spherosomes (4,13,15,16,23). Where and how the fatty acids are subsequently utilized have never been traced even though enzymes of the fl-oxidation sequence were found to be mainly localized in glyoxysomes of castor bean endosperm (7,11) similar to what was observed in ponderosa pine seeds (6).…”

“…Germinating fatty seeds hydrolyze reserve triglycerides to fatty acids and glycerol by lipases associated with fat bodies or spherosomes (4,13,15,16,23). Where and how the fatty acids are subsequently utilized have never been traced even though enzymes of the fl-oxidation sequence were found to be mainly localized in glyoxysomes of castor bean endosperm (7,11) and in mitochondria of pine seeds (21).…”

Microscopy of soybean seeds: cellular and subcellular structure during germination, development and processing with emphasis on lipid bodies

“…Wolf and Baker (1972), utilizing a scanning electron microscope, examined the surfaces of freeze-fractured soybean cotyledons and observed that the oil was contained in small structures (0.3 to 0.5 ^m in diameter), designated as spherosomes, a term used earlier by Saio and Watanabe (1966) to describe the interbody network interspersed with protein bodies in cotyledon cells of soybeans. Evidence from electron-microscopic studies of soybean native fat (Kahn et al, 1960) suggested that jn situ, fat may be enclosed in membranous structures, which collapse as the fat is consumed during seed germination. Webster and Leopold (1977), found that soybean lipid bodies stain uniformly gray after glutaraldehyde-osmium tetroxide fixation and appear to be bounded by a thin electron-dense lamella.…”

“…Wolf and Baker (1975) concluded from their investigations that spherosomes functioned as the major storage sites for soybean oil. However, Kahn et al (1960), believed that the membranes surrounding the native fat contained enzymes required for fat metabolism. Biochemically they found that endogenous as well as added lipase appeared to be preferentially adsorbed on the native fat bodies and detected enzymes such as RNase, protease, lipoxidase, peroxidase and ester phosphatase to be associated with this fraction.…”

“…Isolation of lipid bodies from soybean cotyledons was done using three methods, as described by; Jacks et al (1967), Kahn et al (1960), and Yatsu and Jacks (1972). The methods are based upon sequential centrifugation of a tissue homogenate in an appropriate medium and collecting the resultant floating layer "fat pad" for microscopical examination and chemical analysis.…”