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Complementation of the yeast deletion mutant DeltaNCE103 by members of the beta class of carbonic anhydrases is dependent on carbonic anhydrase activity rather than on antioxidant activity.

ABSTRACT: In recent years, members of the beta class of CAs (carbonic anhydrases) have been shown to complement Delta NCE103, a yeast strain unable to grow under aerobic conditions. The activity required for complementation of Delta NCE103 by tobacco chloroplast CA was studied by site-directed mutagenesis. E196A (Glu196-->Ala), a mutated tobacco CA with low levels of CA activity, complemented Delta NCE103. To determine whether restoration of Delta NCE103 was due to residual levels of CA activity or whether it was related to previously proposed antioxidant activity of CAs [Götz, Gnann and Zimmermann (1999) Yeast 15, 855-864], additional complementation analysis was performed using human CAII, an alpha CA structurally unrelated to the beta class of CAs to which the tobacco protein belongs. Human CAII complemented Delta NCE103, strongly arguing that CA activity is responsible for the complementation of Delta NCE103. Consistent with this conclusion, recombinant NCE103 synthesized in Escherichia coli shows CA activity, and Delta NCE103 expressing the tobacco chloroplast CA exhibits the same sensitivity to H2O2 as the wild-type strain.

SUBMITTER: Clark D

PROVIDER: S-EPMC1224134 | biostudies-other | 2004 May

REPOSITORIES: biostudies-other

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Project description:BackgroundLeptadenia pyrotechnica Forssk. Decne is a member of family Apocynaceae and locally known as 'Khipp'. It is found in dry, sandy habitat of Pakistan and in several other regions around the world including Asia, Tropical Africa, Western Gulf and Mediterranean countries. It has nutritional value, containing 4 % lipids, 23 % proteins, 28 % carbohydrates, 4 % fibers, vitamin E and several minerals. Traditionally, this plant has been used by several communities for pain, different inflammatory and kidney disorders. Ethno-botanical studies have reported the use of L. pyrotechnica in nephrolithiasis, kidney disorders and induction of diuresis, which requires a detailed pharmacological study to validate the folkloric use of L. pyrotechnica as diuretic.MethodsThe 70 % methanolic L. pyrotechnica (Lp.Cr) extract was prepared and qualitatively checked for the presence of various phytochemicals. Phenolic, flavonoid, tannin and saponin contents were quantified. GC-MS analysis of Lp.Cr was also performed. Antioxidant potential of Lp.Cr was evaluated by DPPH, ABTS and nitrite radical scavenging assays. CUPRAC and FRAP assay described the reducing potential of Lp.Cr. Diuretic activity was performed in both acute and prolonged models at different doses followed by the estimation of electrolytes, urea and creatinine levels. The mechanism of diuresis was described by pre-treatment with atropine, l-NAME, indomethacin and carbonic anhydrase inhibition.ResultsLp.Cr. indicated high phenolic and flavonoid contents which correlated with good antioxidant activity. GC-MS analysis showed the presence of 104 compounds from different phytochemical classes. Diuretic activity was performed at 10-300 mg/kg concentrations where the dose of 100 and 300 mg/kg showed good diuretic and saluretic activity comparable to furosemide. Lp.Cr exhibited diuresis both in acute and prolonged study protocols which can be attributed to carbonic anhydrase inhibition, effect on prostaglandins and cholinergic pathways.ConclusionL. pyrotechnica contained several phytochemicals and exhibited good antioxidant activity. It induced diuresis and saluretic activity which was comparable to furosemide at higher doses. Diuretic activity can be attributed to carbonic anhydrase inhibition, prostaglandin synthesis and cholinergic pathways.

Project description:In the mosquito midgut, luminal pH regulation and cellular ion transport processes are important for the digestion of food and maintenance of cellular homeostasis. pH regulation in the mosquito gut is affected by the vectorial movement of the principal ions including bicarbonate/carbonate and protons. As in all metazoans, mosquitoes employ the product of aerobic metabolism carbon dioxide in its bicarbonate/carbonate form as one of the major buffers of cellular and extracellular pH. The conversion of metabolic carbon dioxide to bicarbonate/carbonate is accomplished by a family of enzymes encoded by the carbonic anhydrase gene family. This study characterizes Aedes aegypti carbonic anhydrases using bioinformatic, molecular, and immunohistochemical methods. Our analyses show that there are fourteen Aedes aegypti carbonic anhydrase genes, two of which are expressed as splice variants. The carbonic anhydrases were classified as either integral membrane, peripheral membrane, mitochondrial, secreted, or soluble cytoplasmic proteins. Using polymerase chain reaction and Western blotting, one of the carbonic anhydrases, Aedes aegypti carbonic anhydrase 9, was analyzed and found in each life stage, male/female pupae, male/female adults, and in the female posterior midgut. Next, carbonic anhydrase 9 was analyzed in larvae and adults using confocal microscopy and was detected in the midgut regions. According to our analyses, carbonic anhydrase 9 is a soluble cytoplasmic enzyme found in the alimentary canal of larvae and adults and is expressed throughout the life cycle of the mosquito. Based on previous physiological analyses of adults and larvae, it appears AeCA9 is one of the major carbonic anhydrases involved in producing bicarbonate/carbonate which is involved in pH regulation and ion transport processes in the alimentary canal. Detailed understanding of the molecular bases of ion homeostasis in mosquitoes will provide targets for novel mosquito control strategies into the new millennium.

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Complementation of the yeast deletion mutant DeltaNCE103 by members of the beta class of carbonic anhydrases is dependent on carbonic anhydrase activity rather than on antioxidant activity.

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