Alginic acid metabolism in bacteria. I. Enzymatic formation of unsaturated oligosac-charides and 4-deoxy-L-erythro-5-hexoseulose uronic acid.

Alginic acid, a high molecular weight linear polymer obtained from seaweed, is widely used as an added product to food due to its property of forming highly viscous solutions. Originally described as a polymer of n-mannuronic acid, it has now been demonstrated, by the chemical studies of Fischer and DGrfel (l), to be a ,&l-4-linked polymer of n-mannuronic and L-guluronic acid. The ratio of the two uranic acids vary widely in preparations of alginic acid derived from various species of seaweed. The alginic acid of Macrocystis pyr.ifera, the species examined in the present study, has been reported to have an L-guluronic acid content of 20 to 40% (2). At the present time, little is known of the sequence of the two uranic acids in the polymer. In an attempt to delineate the enzymatic mechanism of alginic acid metabolism, as a prelude to studies on sequence determination, an organism capable of growth on alginic acid as sole carbon source was isolated. The results of metabolic studies with this organism have been reported briefly (3). According to the reaction sequence illustrated in Fig. 1, alginic acid is cleaved by an enzyme fraction referred to as alginase into a series of oligosaccharides containing an unsaturated uranic acid on the nonreducing end of the oligosaccharide chain. These unsaturated oligosaccharides are further degraded with the ultimate production of the monosaccharide, 4-deosy-L-erythro-5-hexoseulose uranic acid.’ The present paper is concerned with the purification and properties of alginase and with further documentation on the identity of the reaction products. The following paper (4) describes the purification of a TPNHlinked dehydrogenase, from alginate-induced Pseudomonas, capable of converting the alginase end product, 4-deoxy-L-erythro-8hexoseulose uranic acid, to 2-keto-3-deoxy-n-gluconate.