Junjiro Ozawa

Pectolytic Enzymes of Exo-Types: Part I. Oligogalacturonide Transeliminase of a Pseudomonas

A bacterium identified as Pseudomonas sp. was found to be a better source of oligogalacturonide transeliminase (OGTE) than Erwinia aroideae.The OGTE of Pseudomonas sp. differed from that of Erwinia aroideae in the following respects: (1) The activity was maximal with tetramer and followed by trimer, dimer and polymers. (2) The OGTE of Pseudomonas sp. degraded the saturated uronides as rapidly as, or a little more rapidly than, the corresponding unsaturated uronides. (3) Calcium ion stimulated considerably the OGTE activity.Both oxidized and reduced acid-soluble pectic acids were resistant to the action of the OGTE.With the purified enzyme preparation, 4-deoxy-5-keto-d-glucuronic acid was the end product of the OGTE action on oligo- and polygalacturonides. 4,5-Unsaturated galacturonic acid is probably the intermediate in the formation of 4-deoxy-5-keto-d-glucuronic acid.

Enzymic Degradation of Pectic Acid Part XI

The present study has been undertaken to determine whether the activity on 4, 5-unsaturated galacturonidic linkage is due to a specific enzyme or to an exopolygalacturonase (exo-PG) which hydrolyzes both saturated and unsaturated galacturonidic linkages. Ratio of activities on 4, 5-unsaturated digalacturonic acid and pectic acid was practically constant before and after heat treatment of the enzyme preparations. The competitive inhibition by galacturonic acid was observed when saturated or unsaturated digalacturonic acid was used as the substrates. The two compounds also inhibited competitively the hydrolysis of the other. These results suggest that the enzyme hydrolyzing 4, 5-unsaturated galacturonidic linkage is identical with exo-PG.

Enzymic Degradation of Pectic Acid Part VII

From the mixture of YPG-ASAP (acid-soluble acid polysaccharides produced from pectic acid by endopolygalacturonase action) and pectic acid, most part of the YPG-ASAP could be recovered by DEAE-cellulose chromatography and by precipitation and washing with acid. From the pectic acid purified by DEAE-cellulose chromatography, about 10% of YPG-ASAP was produced by endopolygalacturonase action. These results indicated that YPG-ASAP is an integral part of pectic acid. Pectic acid purified by DEAE-cellulose chromatography, fractions obtained from pectic acid by precipitation and washing with acid, and original pectic acid all closely resembled each other in contents of YPG-ASAP (ca. 10%) and uronic acid of YPG-ASAP (ca.40%). These results suggested that pectic acid of Citrus Unshiu and that from a commercial citrus pectinic acid are considerably homogeneous in respect of the YPG-ASAP distribution among the individual molecules.