58 THE PLANT CELL WALL 



lates are present. Land mollusks, on the other hand, produce 

 cellulose (and chitinase) themselves, and utilize nutritionally the 

 hydrolysates formed by these enzymes. 



Many micro-organisms produce similar lysins which seem to 

 be enzymic, but have not yet been characterized. Among these 

 are many oxygen sensitive enzymes, which may be converted from 

 inactive to active forms reductively. Such enzymes may account in 

 part, at least, for anaerobic autolysis in bacteria (Bacillus subtilis 

 strains, for example). 



During the germination of Bacillus spores (e.g. B. megaterium, 

 B. cereus), a diamino pimelic acid-alanine-glutamic acid-hexo- 

 samine peptide of MW ca. 10,000, other peptides and free amino 

 acids, are released. The activated spore seems to contain a lytic 

 enzyme (or enzymes) similar in a broad sense to lysozyme, although 

 clearly not identical with it. 



Among cell wall hydrolases in general, both chitinase and 

 cellulase are distinctive as enzymes which attack insoluble substrates. 



The residues from enzymatic attack upon celluloses become 

 progressively more resistant to further enzymatic hydrolysis. 

 If, however, these residues are swelled in phosphoric acid, they 

 once again, become susceptible to cellulase. Increased resistance 

 in residues and restoration of susceptibility correlate well with 

 the increased crystallinity of hydrolytic residues and the disordering 

 effect of phosphoric acid. It seems clear, therefore, that cellulase 

 attacks amorphous regions in celluloses where interaction between 

 functional groups in the polysaccharide and solvent or other polar 

 molecules will be strongest. 



Both cellulase and chitinase are activated by small amounts of 

 additives. Cellulase is activated by crystalline bovine plasma 

 albumin, p-lactoglobulin, pepsin, lysozyme, and gelatin (at 50 mg/1). 

 Albumin, at 30 mg/1. increased cellulolysis five-fold. Similarly 

 bovine serum albumin increases chitinases actively two-to five-fold. 



The discussion, thus far, has indicated the significance and 

 unusual properties of some wall-lysing enzymes. To conclude 

 this consideration of cell wall breakdown we will review briefly 

 the important representative lytic enzymes, their reactions and 

 some organisms in which they have been found. 



