364 ENZYMES 



a concentrated solution of glucose, the disaccharide iso-maltose 

 was produced ; later it was shown that the disaccharide iso- 

 lactose could be synthesized from galactose and glucose by the 

 action of lactase from Kefir. Since then a large number of 

 enzymatic syntheses have been effected, amongst them being 

 included the synthesis of maltose itself by the action of 

 emulsin on a concentrated solution of glucose which was 

 described by E. F. Armstrong, and also the formation of 

 glycogen from a 30 per cent solution of fructose by yeast- 

 extract free from glycogen,* a reaction which most probably 

 involves the conversion of fructose into glucose. 



The following experiment has been devised by Bayliss j- 

 for demonstrating the synthetic action of emulsin in the pro- 

 duction of a glucoside : 



Two solutions are required : (a) a 15 per cent solution of 

 hydroquinone in glycerol, and () a 50 per cent aqueous 

 solution of glucose mixed with an equal volume of glycerol. 

 The two solutions (#) and () are mixed in equal proportions, 

 and about 2 per cent of emulsin are added, and the mixture is 

 ground in a mortar and then warmed to 38 to make it less 

 viscid. Ten per cent of the solution are then delivered by 

 means of a pipette into a series of test tubes, a little toluene 

 is added to each, and after displacing the air above the liquid 

 by COp, the tubes are sealed up in a blow-pipe, but this is 

 not absolutely necessary ; if this is not done the liquid may 

 darken owing to oxidation of the hydroquinone, but on adding 

 a small quantity of sodium bisulphite the colour is discharged. 



One sample is at once diluted to 50 c.c., and filtered, and 

 its rotation is measured in the polarimeter. The other tubes 

 are placed horizontally in an incubator, and samples are with- 

 drawn every three or four days ; the tubes are cracked across, 

 and their contents are rinsed into a 50 c.c. flask. 



The initial rotation of about + 3 will be reduced to 

 0-5 in a week, indicating a synthesis of 25 to 30 per cent of 

 arbutin. 



To prove that the diminution of rotation is not due to 

 destruction of glucose the glucoside may be reconverted into 



*Cremer: "Ber. deut. chem. Gesells.," 1899, 32, 2062. See also Meyer: 

 "Bot. Ztg.," 1899, 57, 313. 



f Bayliss : " J. Physiol.," 1912, 43, Proceedings, XL. 



