Enzymes 159 



tail, and no opinion can be expressed as to whether or not it 

 is of an enzymatic nature. 



It must be remarked here that myeloid granules show 

 peculiar reactions when incubated with phenolic substances 

 (especially naphthols) under the conditions mentioned. If 

 the solutions used are stale and somewhat colored by spon- 

 taneous oxidation, an intense purple-black coloration of the 

 granules becomes evident within 10 minutes. With fresh 

 solutions, darkening of the granules is, absent or minimal; 

 however, the binding of naphthol by the granules can easily 

 be demonstrated by suitable reactions, such as azo-coupling 

 or the Gibbs reaction (formation of indophenol blue on ex- 

 posure to dichloro- or dibromoquinoneimide ) . Moreover, the 

 naphthol-treated granules exhibit unusual staining reactions. 

 They will stain intensely with basic dyes^^- ^^ and with fat 

 dyes, such as Sudan III (de Bruijn).^^ Even in paraffin sec- 

 tions, myeloid granules will stain intensely with Sudan III 

 or Sudan Black B after 10 minutes' exposure to an alkalized, 

 saturated aqueous solution of naphthol. The nature of this 

 "phenolophilia" or "naphtholophilia"^^ is not clear (quinone- 

 ethylenic condensation?). 



C ) Dopa oxidase.— 



In 1916 Bloch and Ryhiner^^ found that the basal layers 

 of the epidermis, leucocytes, and other tissue elements con- 

 tain an enzyme which oxidizes Z-3,4-dihydroxyphenylalanin 

 (dopa) to a blackish pigment, indistinguishable from natural 

 melanin. In subsequent papers'^^ Bloch offered good evidence 

 that dopa is attacked by two different enzymes: (1) a non- 

 specific phenol oxidase which is relatively resistant to various 



53. Graham, G. S.: J. M. Research, 35:231, 1916-17. 



54. De Bruijn, P. P. H.: Acta Neerland. morph. norm, et path., 2:232, 



1939. 



55. Bloch, B., and Ryhiner, P.: Ztschr. f. d. ges. exper. Med., 5:179, 



191&-17. 



56. Bloch, B., and Loffler, W.: Deutsches Arch. f. klin. Med., 121:262, 

 1916-17; Bloch, B.: Ztschr. f. physiol. Chem., 98:226, 1917; Bloch, B.: 

 Arch. f. Dermat. u. Syph., 124:129, 1917; Bloch B.: Am. J. M. Sc, 177:609, 

 1929; Bloch, B., and Schaaf, F.: Klin. Wchnschr., 11:10, 1932. 



