ATP citrate lyase (EC 4.1.3.8) This enzyme was first described by Srere and Lipmann (18) in pigeon liver and has been further characterized in chicken and rat liver (17). It is widely distributed in animal tissues and shows high activity in liver, adipose tissue, lactating mammary glands, brain and adrenal tissue (7,16,17). ACL was found to be localized in the cytosol (16). (-)-Hydroxycitrate has been shown to be a potent and specific competitive inhibitor of the enzyme (17). In animals, particularly those on a high carbohydrate diet, ACL plays an important role in fatty acid synthesis (17). Citrate generated in the mitochondria is cleaved by ACL in the cytosol, providing the acetyl-CoA used there in fatty acid biogenesis. Accordingly, exogenous citrate is a good precursor of fatty acids and (-)-hydroxycitrate is an inhibitor of fatty acid synthesis from suitable precursors in vivo (17 MATERIALS AND METHODS Castor bean seeds (Ricinus communis cv. Hale) were soaked overnight in running tap water, sown in water-saturated Vermiculite, and grown at 30 C in darkness. Endosperms were removed from seedlings, rinsed in ice cold water, and kept on ice until homogenization.Crude extracts were prepared by grinding the endosperms from five seedlings in 5 ml 0.1 M Tricine-KOH (pH 7.5) containing 10 mm mercaptoethanol and 0.1% Triton X-100 in a chilled mortar. The resulting slurry was centrifuged at 30,000g for 20 min in a refrigerated centrifuge. The fat layer and pellet were discarded and the supernatant solutions used as the crude extract. Extracts of endosperm from ripening castor bean at the stage when the testae were just beginning to color were prepared in the same way. Seeds of watermelon (Citrullus vulgaris), sweet corn (Zea mays), soybean (Glycine max), sunflower (Helianthus annuus), peanut (Arachis hypogea), and mung bean (Phaseolus aureus) were germinated as for castor beans. For the preparation of crude extracts, the roots and lower half of the hypocotyl were removed and the rest of the seedling homogenized and centrifuged as described above. From sweet corn the coleoptile (including the primary leaf) and scutellum were extracted. In preparing castor bean extract for the time course studies some sand was added to facilitate grinding.Total citrate in the endosperm tissue was extracted in dilute HClO4 and estimated using the malate dehydrogenase coupled assay with commercial bacterial citrate lyase (2). Protein concentrations were determined by the biuret reaction or a modified Lowry procedure (3).For the preparation of organelles, 20 isolated endosperms were chopped with razor blades in 14 ml 0.15 M Tricine-KOH (pH 7.5) containing 10 mm 2-mercaptoethanol, I mm EDTA, and 20o sucrose (w/w). The homogenate was passed through three layers of nylon cloth and 10 ml of the filtrate was layered on top of a linear sucrose gradient. The gradient consisted of 40 ml 30 to 60%o sucrose containing 10 mm citrate and 1 mm EDTA, over a cushion of 62% sucrose, and topped by 4 ml 30%o sucrose containing the same additives...
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
From cell cultures of Haplopappus gracilis, an enzyme, catalyzing the glucosylation of cyanidin at the 3 position using uridine diphosphate-D-glucose (UDPG) as glucosyl-donor, has been isolated and purified 50-fold. The enzyme was not specific for cyanidin alone, but also glucosylated other anthocyanidins and flavonols in position 3. However, apigenin, luteolin, naringenin and dihydroquercetin were not glucosylated. The reaction has an optimum pH of approximately 8, and the apparent K m values for UDPG and cyanidin were 0.5 and 0.33 mM respectively. The enzyme reaction is strongly inhibited by cyanidin (above 0.25 mM).
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.