酵素によるペクチン酸の分解(第13報)

ペクチン酸からジガラクチュロン酸を生成する新しいエキソポリガラクチュロナーゼについて

抄録

(1) The exopolygalacturonase of Erwinia aroideae was purified by treating with Duolite CS-101 and DEAE-cellulose chromatography. (2) Its mode of action was studied with the purified enzyme. It was shown that the enzyme removed digalacturonic acid from the non-reducing end of the substrate molecules. It was called digalacturonopoly-galacturonase (polygalacturonide digalacturonohydrolase) while the exopolygalacturonase so far known was designated as galacturonopolygalacturonase (polygalacturonide galacturo-nohydrolase). (3) Trigalacturonic acid was degraded, though at a far lower rate than oligogalacturonic acid homologues of chain length of 4 units or more and polygalacturonides. Digalacturonic acid was resistant to the enzyme action. (4) Unsaturated oligoand polygalacturonides were also degraded, 4, 5-unsaturated digalacturonic acid being formed as a product. The rate of hydrolysis was found to be lower than for the oligoand polygalacturonides having no unsaturated galacturonic acid residue. (5) When pectic acid, acid-soluble pectic acid, tetragalacturonic acid and unsaturated acid-soluble pectic acid were used as substrates, pH optima were observed around 7. 2. With trigalacturonic acid as substrate the enzymatic activity showed no sharp optimum in the range of pH 4. 8 to 7. 0. (6) Calcium ion had no effect on the enzyme activity.