, Volume 65, Issue 11, pp 621-631

Isolaton, partial purification and characterization of a potato peel glycoalkaloid glycosidase

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Abstract

The enzymes involved in the hydrolysis of the rhamnose moieties fromα-chaconine were isolated and partially purified by ammonium sulfate precipitation from the peels of Kennebec and Wauseon potatoes. Enzyme activity was found to be present in the 60 to 80% ammonium sulfate precipitate. Enzyme activity was increased by the use of non-ionic detergents with a mixture of Triton X-100:Triton CF-54 providing the greatest increase in activity. The pH and temperature optimums for the enzymes from both varieties were found to be 6.0 and 42 C, respectively. The route ofα-chaconine metabolism (either through B1-or B2-chaconine) was dependent upon incubation temperature. The effect of substrate concentration on enzyme activity was determined for both varieties and the Kms calculated from Lineweaver-Burke double reciprocal plots. The Km values for the Kennebec and Wauseon rhamnosidases were found to be 9.2×10−4 and 1.7×10−5M, respectively.

Compendio

Las enzimas que intervienen en la hidrólisis de las fracciones de ramnosa de laα-chaconina fueron aisladas y parcialmente purificadas por precipitación con sufato de amonio, a partir de cáscaras de papa de las variedades Kennebec y Wauseon. Se encontró presencia de actividad enzimática en la fracción saturada (0,6 a 0,8) de sulfato de amonio. La actividad enzimática se incrementó usando detergentes no iónicos con una mezcla de Triton X-100: Triton CF-54, que proporciona, el mayor incremento de la actividad. El óptimo de pH y temperatura para las enzimas de ambas variedades fué de 6,0 y 42 C respectivamente. La ruta del metabolismo de laα-chaconina (sea ésta a través de chaconina B1 ó B2) dependió de la temperatura de incubación. Se determinó) el efecto de la concentración del substrato sobre la actividad enzimática para ambas variedades y el Kms se calculó por la función recíproca doble Lineweaver-Burke. Se encontró que los valores Km para las ramnosidasas de Kennebec y Wauseon fueron de 9,2×10−4 y l,7×10−5M, respectivamente.