Polygalacturonase converter

Knegt,E., Vermeer,E, Pak,C and Bruinsma,J (1991) Function of the polygalacturonase converter in ripening tomato finit. Physiologia Plantarum. 82.237-242. 

Pressey,R (1984) Purification and characterisation of tomato polygalacturonase converter. European J Biochemistry. 144.217-221. 

Polygalacturonase (PG) is widely distributed in higher plants. The richest plant source of PG is ripe tomato fruit. Extacts of tomatoes contain two forms of the enzyme (PG I and PG II) which differ markedly in molecular size and stability to heat. A protein (PG converter) has been isolated from tomatoes that reacts with PG II to form PG I. PG II can be recovered by treating PG I with mild alkali (pH 11). Both tomato enzymes are endo-PG s. Some fruits that soften markedly during ripening such as pears and freestone peaches contain not only endo-PG but also exo-PG. Other fruits such as apples and clingstone peaches contain only exo-PG, consistent with slow softening characteristics. 

M NaCl at pH 5.5 to remove most of the FG II and other soluble components. The insoluble fraction was then extracted with 1.2 M NaCl at pH 6. The extract was concentrated by ultrafiltration, adjusted to pH 5, and heated 7 min. at 100 C to inactivate the polygalacturonases. The FG converter in the heated solution was then purified by chromatography on Sephacryl S-200 and Folyanion SI and by chromatofocusing on a Mono F column. A 28-fold increase in the specific activity of the converter was achieved with an 81% recovery of total activity (Table I). 

Pectic Acids and Pectins.—Pectin has been converted into a j-triazinyl derivative having C-6 of the hexuronic acid residues incorporated into the heterocyclic ring. The actions of polygalacturonase and acid on the derivative were investigated. 

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