A fouth mlcular form of a-galactosldase, designted Liv, an alkaine a-galactoshldm, was isolated from leaves of Cwwbita pepo and purIed 165-fohld It was active over a narrow pH range with optimal hydrosi of p-nitrophenyl-a-D-galactoslde ad stachyose at pH 7.5. In 10 mlHlmolar trietha m hydrochlorlde-NaOH (pH 7.5) or 10 mmlar Hepes-NaOH (pH 7.5), hydrolytic activity was virtually eUminated, but the addition of low concentrations of either ethylenedlaminetetraacetate or citrate to these buffers restored actvity almost completely. Partial restoration of acti was also observed, but at higher concentrations, with pyruvate and malate. Similar effects were found for stachyose hydrolysis, but In addition some Inhibition of L1v In Mcdlvaine buffer, possibly due to the high phosphate concentration, was observed with this substrate. It Is questionable whether the organic acid anio possess any regulatory control of Liv in vivo. It was possible that the results reflected the ability of these anions, and ethylenediaminetetrascetate, to restore Liv activity through coordination with some toxic cation Introduced as a buffer contaminant.The raffmose family of D-galactose-containing oligosaccharides (5) constitute a major portion of the soluble sugar translocated in a number of plant families (24) and they occur even more widely distributed in storage organs such as seeds, roots, and tubers (8).It is generally acknowledged that a-galactosidases (EC 3.2
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