XX CONTENTS 



3 Peroxidases and Dihydroxymaleic Acid Oxidase 419 



3.1 Introduction 419 



3.2 Horse-radish Peroxidase 420 



3.2.1 Isolation 420 



3.2.2 Absorption Spectra and Magnet ochemical Proper- 

 ties of Peroxidase and of Its Compounds 420 



3.2.3 Inhibitors 421 



3.2.4 Kinetics and Estimation 422 



3.2.5 Protein of Peroxidase 424 



3.2.6 Linkage of Prosthetic Group and Protein 425 



3.3 Other Plant Peroxidases 428 



3.4 Milk Peroxidase 429 



3.5 Peroxidase of Adrenal Medulla 430 



3.6 Peroxidase of Leucocytes (Myeloperoxidase, "Verdoperox- 

 idase") 430 



3.7 Cytochrome c Peroxidase 432 



3.8 Dihydroxymaleic Acid Oxidase 433 



3.9 Biological Function of Peroxidases 434 



3.9.1 Plant Peroxidases 434 



3.9.2 Animal Peroxidases 435 



4 Mode of Catalatic and Peroxidative Action 436 



4.1 Peroxidase and Dihydroxymaleic Acid Oxidase 436 



4.1.1 Mode of Action of Peroxidase 436 



4.1.2 Mode of Action of Dihydroxymaleic Acid Oxidase . 437 



4.2 Catalase 439 



4.2.1 Radical Chain Theory 439 



4.2.2 Keilin's Theory 440 



4.2.3 Theories of Stern and Sumner 442 



4.2.4 Attempts at a New Theory 442 



4.2.5 Anticatalases and Philocatalases 443 



4.2.6 "Coupled Oxidation" of Alcohol 444 



5 Enzymes Possibly of Hemoprotein Nature 446 



5.1 Hydrogenase 446 



5.2 Nitrogen Fixation 448 



5.3 Possible Hematin Nature of Catalysts in Photosynthetic 

 Processes 450 



X. Chemical Mechanism of Bile Pigment Formation and Other 



Irreversible Alterations of Hemoglobin 453 



1 Introduction and Nomenclature 453 



2 Model Experiments on Bile Pigment Formation. Verdohemochromes 456 



2.1 Introduction 456 



2.2 Bile Pigments Formed from Verdohemochrome 459 



2.3 Preparation and Properties of Verdohemochromes 461 



2.4 Structure of Verdoheme 464 



2.5 Mechanism of Formation of Verdohemochromes 467 



3 Photochemical Formation of Bile Pigments from Porphyrin Metal 

 Complexes 471 



4 Formation of Biliverdin from Hemoglobin in Vitro. Choleglobin. . . 471 



4.1 Introduction 471 



4.2 Properties of Choleglobin 472 



4.2.1 Spectroscopic Properties 472 



