Invertases of carnation petals. Partial purification, characterization and changes in activity during petal growth

Abstract

Carnation ( Dianthus caryophyllus L. cv. White Sim) petals contained two distinct invertases (EC 3.2.1.26) based on chromatographic behavior on DEAE‐cellulose. Both are soluble in 20 m M sodium phosphate buffer (pH 6.5) and exhibit acid pH optimum of 5.5. Extraction of a cell wall preparation from petals with 1 M NaCl released little additional activity. Furthermore, only traces of activity remained associated with the NaCl‐extracted cell wall preparation. One of the soluble invertases, representing over 75% of the total activity, was partially purified by (NH 4 ) 2 SO 4 fractionation and sequential chromatography over diethylaminoethyl‐cellulose, concanavalin‐A sepharose and polyacrylamide P‐200. The enzyme was purified 38‐fold with a recovery of 12%. It had an apparent native molecular weight of 215 kDa. The partially purified invertase is a β‐fructofuranosidase (EC 3.2.1.26) based on its specificity for sucrose. The K m for sucrose was 3.3 m M . Accumulation of reducing sugars and increased invertase activity during expansive petal growth indicates that sucrose is the major source of carbon for petal growth.