Biochemical properties of alpha-amylase from peel of Citrus sinensis cv. Abosora.
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.
Mohamed
Saleh Ahmed
SA
Biochemistry Department, Faculty of Science, King Abdulaziz University, Jeddah 21589, Kingdom of Saudi Arabia. saleh38@hotmail.com
Drees
Ehab A
EA
El-Badry
Mohamed O
MO
Fahmy
Afaf S
AS
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*
D008670:Metals; D000516:alpha-Amylases