title: Biochemical properties of alpha-amylase from peel of Citrus sinensis cv. Abosora.
abstract: alpha-Amylase activity was screened in the peel, as waste fruit, of 13 species and cultivars of Egyptian citrus. The species Citrus sinensis cv. Abosora had the highest activity. alpha-Amylase AI from Abosora peel was purified to homogeneity using anion and cation-exchange, and gel filtration chromatographies. Molecular weight of alpha-amylase AI was found to be 42 kDa. The hydrolysis properties of alpha-amylase AI toward different substrates indicated that corn starch is the best substrate. The alpha-amylase had the highest activity toward glycogen compared with amylopectin and dextrin. Potato starch had low affinity toward alpha-amylase AI but it did not hydrolyze beta-cyclodextrin and dextran. Apparent Km for alpha-amylase AI was 5 mg (0.5%) starch/ml. alpha-Amylase AI showed optimum activity at pH 5.6 and 40 degrees C. The enzyme was thermally stable up to 40 degrees C and inactivated at 70 degrees C. The effect of mono and divalent metal ions were tested for the alpha-amylase AI. Ba2+ was found to have activating effect, where as Li+ had negligible effect on activity. The other metals caused inhibition effect. Activity of the alpha-amylase AI was increased one and half in the presence of 4 mM Ca2+ and was found to be partially inactivated at 10 mM Ca2+. The reduction of starch viscosity indicated that the enzyme is endoamylase. The results suggested that, in addition to citrus peel is a rich source of pectins and flavanoids, alpha-amylase AI from orange peel could be involved in the development and ripening of citrus fruit and may be used for juice processing.
authors: Biochemistry Department, Faculty of Science, King Abdulaziz University, Jeddah 21589, Kingdom of Saudi Arabia. saleh38@hotmail.com
authors: Saleh Ahmed
authors: SA
authors: Mohamed
authors: Ehab A
authors: EA
authors: Drees
authors: Mohamed O
authors: MO
authors: El-Badry
authors: Afaf S
authors: AS
authors: Fahmy
mesh_terms: D032084:Citrus sinensis / Q000201:enzymology*; D004789:Enzyme Activation / Q000187:drug effects; D004795:Enzyme Stability; D005638:Fruit / Q000201:enzymology*; D006863:Hydrogen-Ion Concentration; D008670:Metals / Q000494:pharmacology; D008970:Molecular Weight; D013696:Temperature; D000516:alpha-Amylases / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism*
chemical_list: D008670:Metals; D000516:alpha-Amylases