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A large number of bacteria and fungi secrete extracellularly the enzyme complex often termed 'pectinase', which causes the rapid disintegration of plant tissue and is consideredtheprimaryinstrument of the attack on plant tissues by these microorganisms. The action of pectinase on a solution of pectin results in the following changes: (a) a rapid lowering of the viscosity of the solution; (b) a failure of the solution to form a gel on the addition of ethanol or solutions of calcium salts, only a gelatinous precipitate or a cloudy suspension being formed; (c) an increase in the titratable acidity ofthe solution; (d) an increase in the reducing power of the solution, as measured by the iodine-reducing value. These effects are now considered to be due to the action oftwo distinct enzymes: 'pectin esterase' and 'polygalacturonase'. The increase in acidity is due to the demethylation of the pectin by pectin esterase (Holden, 1948). The lowering of viscosity, failure of gelation, and increase in reducing power are due to the degradation of pectin by polygalacturonase which has beeni claimed (Jansen & MacDonnell, 1945) to act only very slowly on true pectin but rapidly on demethylated pectin (pectic acid). Changes in viscosity and gelling properties are brought about fairly rapidly even by very weak enzyme preparations, but marked changes in reducing power only appear with active preparations. The mechanism of the demethylation of pectin to pectic acid and the action ofpolygalacturonase have been extensively investigated and the literature has been reviewed by Phaff & Joslyn (1947). The main object of the present investigation has been to study by chromatographic methods the products arising from the degradation of pectic acid by polygalacturonase.

The chromatographic examination of the products of the action of pectinase on pectin