52 BACTERIAL ENZYMES 



systematic bacteriology (Chap. II). The specificity of thfe 

 polysaccharide-splitting enzymes depends upon the nature of 

 the linkages between the sugar units of the polysaccharide 

 chain. CI. welchii, for example, cannot hydrolyse starch 

 unless it is first grown in the presence of starch which then 

 evokes the production of the enzyme. The organism grown 

 in the presence of starch can also hydrolyse maltose and 

 glycogen. Likewise, if the organism is grown in the presence 

 of maltose, then it gains the power to hydrolyse starch and 

 glycogen. Consequently the enzyme or enzymes necessary 

 for the hydrolysis of starch, glycogen, or maltose cannot be 

 produced unless growth takes place in the presence of any one 

 of these carbohydrates. Growth in glucose does not produce 

 the enzyme. Full investigation has not been made, but the 

 assumption is that we are dealing with the production of an 

 adaptive enzyme (Chap. IV), specific for the hydrolysis of the 

 maltose linkage. The breakdown of starch by CI. aceto- 

 hutylicum is accomplished by the production of two enzymes ; 

 first, an amylase which hydrolyses the starch to maltose, and, 

 secondly, a maltase which completes the hydrolysis of maltose 

 to glucose. Cellulose is attacked by a variety of organisms 

 normally found in the rumen and on plant tissues. Cellulo- 

 bacillus myxogenes produces two enzymes responsible for the 

 hydrolysis of cellulose, the first, cellulase, hydrolyses cellulose 

 (see p. 120) to cellobiose, and the second, cellobiase, completes 

 the hydrolysis of cellobiose to glucose. 



5. Deamination 



The removal of — NH2 from the molecule of an amino-acid, 

 amine, etc., is seldom achieved in a single step. We have 

 already had two examples of deamination occurring in two 

 steps: the amino-acid oxidase of Pr. vulgaris, and the 

 L-glutamic acid deaminase of Esch. coU, where the first step 

 is a dehydrogenation of the amino-acid to the corresponding 

 imino-acid which then undergoes spontaneous hydrolysis to 

 the corresponding keto-acid liberating ammonia: 



