Submitted to: American Society of Plant Physiologists Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 3/20/2000
Publication Date: N/A
Technical Abstract: A soluble acid invertase from six-week old sugarbeet roots was partially purified and some of its biochemical and physical properties were characterized. This invertase isoenzyme has a Km for sucrose of 8.9 mM and was not inhibited by fructose. The enzyme exhibits a plateau of activity at pH 5.0 to 5.5 and was activated 7.5-fold at pH 3.0, possibly due to the loss or inactivation of an inhibitor. The enzyme was unstable at pH values equal to or greater than 7.5 at high ionic strength. While short incubations at pH 3.0 and 4.7 caused minor losses in activity, prolonged exposures to these pH conditions partially activated the enzyme. The enzyme exhibited a sharp temperature optimum at 35oC. At temperatures above or below this optimum, enzyme activity declined rapidly, although 16% of its activity still remained at 5oC. Rapid and irreversible inactivation occurred at 40oC and above. Partial inactivation was observed at temperatures of 40oC to 50oC, while a complete inactivation of the enzyme was achieved at 55oC and above. Scholarship for FLF was provided by CAPES/MEC (Brazil).