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Query: UMLS:C0009443 (cold)
 92,137 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Galactolipase activity in chloroplasts of several chill-resistant plants was found to be very low [0.02-0.13 mumol free fatty acid (FFA) liberated min-1 mg protein-1] or not detected. The same phenomenon was observed for soybean and members of the Cucurbitaceae such as cucumber, pumpkin, melon and squash. Since, following cold storage of cucumber leaves, the levels of monogalactosyl-diacylglycerol and digalactosyl-diacylglycerol in chloroplasts decrease while those of FFA accumulate it seems likely that in these typical chill-sensitive plants galactolipase is present but inactivated during isolation procedure. The low galactolipase activity in chloroplasts was accompanied by a relatively low FFA content ranging from 0.05 mumol to 0.30 mumol FFA mg chlorophyll (Chl)-1. However, both pea and horse bean chloroplasts (with low galactolipase activity) exhibit about 0.45 mumol FFA mg Chl-1. Elevated galactolipase activity was observed in chloroplasts of most chill-sensitive species (ranging from 0.31 mumol to 1.32 mumol FFA liberated min-1 mg protein-1) as well as in chloroplasts from broad bean, a member of a chill-resistant species (1.26 mumol FFA liberated min-1 mg protein-1). In addition in this latter group of plants FFA level in chloroplasts often did not fit the galactolipase activity. The results suggest that there exists a tendency for chilling tolerance of plants to decrease both galactolipase activity and FFA level. However, in some plant species with elevated galactolipase activity the chloroplast FFA level does not correlate with enzyme activity.
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PMID:Comparison of galactolipase activity and free fatty acid levels in chloroplasts of chill-sensitive and chill-resistant plants. 359 13

1. Both galactolipase treatment of tomato chloroplasts and the cold and dark storage of leaves induce a large degradation of chloroplast monogalactosyl diacylglycerol and digalactosyl diacylglycerol as well as an accumulatwon of free fatty acids accompanied by the inhibition of Hill reaction activity with water as electron donor. All these changes are reversed upon illumination of the leaves. 2. Inhibition of diphenylcarbazide (DPC) leads to dichlorophenolindophenol (DCIP) activity by free fatty acids released following galactolipase treatment of chloroplasts isolated from either fresh or cold and dark-stored and illuminated leaves is almost completely reversed by either bovine serum albumin or Mn2+, while that in chloroplasts from the cold and dark-stored leaves is reversed by bovine serum albumin and Mn2+ only up to about 60 and 25%, respectively. 3. Fatty acids released during the treatment of chloroplasts with galactolipase affect the electron transport mainly in the same site as exogenous unsaturated fatty acids do, while those released due to endogenous galactolipase activity appear to affect also in the region damaged by either Tris washing of chloroplasts or the cold and dark treatment of leaves. 4. The loss of manganese from chloroplasts (Kaniuga, Z., Zabek, J. and Sochanowicz, B. (1978) Planta 144, 49-56) seems to be the main reason of cold and dark-induced inactivation of Hill reaction activity in chloroplasts of chilling-sensitive plants, while both the degradation of galactolipids and the accumulation of fatty acids are of secondary importance.
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PMID:Photosynthetic apparatus in chilling-sensitive plants. VII. Comparison of the effect of galactolipase treatment of chloroplasts and cold-dark storage of leaves on photosynthetic electron flow. 735 80

The role of acyl lipids in the in vitro stabilization of the oligomeric form of light-harvesting complex II of winter rye (Secale cereale L. cv Muskateer) grown at 5 or 20 degrees C was investigated. Purified light-harvesting complex II was enzymically delipidated to various extents by treatment with the following lipolytic enzymes: phospholipase C, phospholipase A(2), and galactolipase. Complete removal of phosphatidylcholine had no effect on the stability of the oligomeric form, whereas the removal of phosphatidylcholine plus phosphatidylglycerol caused a decrease in the ratio of oligomeric:monomeric forms from 1.86 +/- 0.17 to 0.85 +/- 0.17 and 3.51 +/- 0.82 to 0.81 +/- 0.29 for purified cold-hardened and nonhardened light-harvesting complex II, respectively, with no change in free pigment content. Incubation of delipidated cold-hardened or nonhardened light-harvesting complex with purified thylakoid phosphatidylglycerol containing trans-Delta(3)-hexadecenoic acid resulted in 48% reconstitution of the oligomeric form on a total chlorophyll basis with an oligomer:monomer of about 1.90. Incubation in the presence of di- 16:0 or di- 18:1 phosphatidylglycerol, phosphatidylcholine, monogalactosyldiacylglyceride, or digalactosyldiacylglyceride caused no oligomerization, but rather a further destabilization of the monomeric form. These lipid-dependent structural changes were correlated with significant changes in the 77K fluorescence emission spectra for purified light-harvesting complex II. We conclude that the stabilization of the supramolecular organization of light-harvesting complex II from rye is specifically dependent upon molecular species of phosphatidylglycerol containing trans-Delta(3)-hexadecenoic acid.
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PMID:The Role of Acyl Lipids in Reconstitution of Lipid-Depleted Light-Harvesting Complex II from Cold-Hardened and Nonhardened Rye. 1665 78