General Biochemistry of the Trehaloses

The existence of an enzyme, trehalase, capable of splitting the a,a-trehalose molecule was demonstrated by Bourquelot. The biochemistry of the enzyme has been reviewed by Myrhack. The presence of trehalase in fungi and various animals was demonstrated by Willstaedt and Borgkrd.1 1 Candy and Kilby obtained a trehalase from an extract of fat body-tissue of locusts. 

A convenient source of trehalase is bakers yeast. It is an a-n-glu-cosidase distinguishable from maltase by the damage suffered by the maltase on yeast storage. a,a-Trehalose added to bakers yeast is fermented (in aqueous suspension), but the a,a-trehalose stored within the yeast remains unaffected. Evidently, there is a spatial separation between yeast trehalase and its stored trehalose. The enzyme may be at the cell 

The pH optimum of trehalase varies according to its source. This was known for different yeasts at the time of Myrback s review. Frerejacque obtained material with trehalase activity from swine intestinal mucosa, beef liver, snail digestive Juice, and sheep small intestine, all preparations having a pH optimum of 6. 

The pH optimum for the fermentation of a,a-trehalose by living yeast differs from that of n-glucose fermentation, being narrow at a pH of about 5. This optimum coincides with that of brewers -yeast trehalase and indicates that hydrolytic splitting of the a,a-trehalose molecule may precede fermentation of a,a-trehalose. Bakers yeast trehalase is less stable than brewers yeast trehalase. Courtois and Valentino showed that the tetraaldehyde produced by the periodate oxidation of a,a-tre-halose is not attacked by trehalase. On the other hand, Helferich and Stryk showed that 6-0-(methylsulfonyl)-a,a-trehalose is attacked. Hydrolysis of a,a-trehalose by almond emulsin took place to the extent of 27%, and of the monomesyl ester to the extent of 15.5%, after 6,120 minutes. The corresponding figures for yeast extract were 12.1% and 8.3%, respectively, after 7,200 minutes. 

Myrback reported that very old, dried yeast ferments a,a-trehalose as fast as, if not faster than, it does D-glucose. Fresh, living yeast-cells ferment D-glucose more quickly than they do a,a-trehalose. However, O Connor showed that, with the fungus Fusarium Uni Bolley, fermentation of a,a-trehalose is more rapid and abundant on a,a-trehalose than on D-glucose. 

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