Structural Factors in Polymerization: The 

 Aiatrix in Aromatic Biopolymer Formation 



S. M. SIEGEL 



Union Carbide Research Institute 

 White Plains, New York 



ALTHOUGH THE HIGHEST EXPRESSION of biological spccificity may reside in cellu- 

 > lar polynucleotides, an important motle of expression of genetic and 

 physiological uniqueness may also be found in biochemical products somewhat 

 removed from the immediate necessities for life, namely the 'secondary' or 

 'metaplasmic' deri\atives of the cell. Indeed, the subtleties of nucleic acid struc- 

 ture and function, now in the most elementary stages of elucidation, are expressed 

 with great amplification in the specific syntheses associated with formation of 

 melanin, lignin, rubber, and other polymeric materials. It is, therefore, of no little 

 importance to recognize that the biosynthetic pathways for the manufacture of 

 some of these by-products are dependent upon specific structures other than those 

 ordinarily involved in enzymic catalysis. It is hoped that the investigations and 

 findings to be detailed here will, in fact, contribute to a broadening of the con- 

 cept of 'biocatalysis' to include the reaction- and polymerization-directing ('ma- 

 trix") properties of non-enzymic macromolecules. 



Development of the matrix concept has been intimately associated with studies 

 on the biosynthesis of lignin' and other di- or polymeric compounds of aromatic 

 derivation. An important part of this association has been the use of model sys- 

 tems which trace their origin to the usual organ and tissue systems whose be- 

 havior is difficultly interpretable at best, and whose reduction to the present 

 minimal form is in itself an object of interest from the viewpoint of the 

 experimentalist. 



EVOLUTION OF A MODEL SYSTEM: LIGNIN SYNTHESIS AND THE POLYSACCHARIDE ^L\TRIX 



Behavior of Peroxidase In Situ and In Vitro. The demonstration of a 

 system in plants able to convert appropriate aromatic compounds into lignins 

 grew out of initial observations which dealt with the differences in enzymatic 

 peroxidation of phenols and aromatic amines by crystalline horseradish peroxidase 

 and by peroxidases retained /;/ sitii in tissue slices from a variety of plant species; 

 color and solubility of product were initially noted, hence non-chlorophyllous 



1 Brauns (4) reviews the chemistry of lignins; Siegel (30) emphasizes the jihysiological and 

 biochemical aspects of lignin formation. 



37 



