CHAPTER 15 



Nucleases and Enzymes Attacking Nucleic Acid Components 



G. SCHMIDT 



Page 



I. Introduction 556 



II. Enzymes Ciitahziiig the Cleavage of Bonds Between Nucleotides 558 



1. Ribonucleases 558 



a. Pancreas Ribonuclease (Ribonuclease I) 558 



b. Other Ribonucleases • 575 



2. Deoxyribonucleases 576 



a. Pancreas Deoxj'ribonuclease (Deoxyribonuclease I) 576 



b. Other Deoxyribonucleases 584 



3. "Unspecific" Phosphodiesterases 585 



a. Snake Venom Phosphodiesterases 585 



b. "Phosphodiesterase" of Intestinal Mucosa 588 



III. Enzymes Catalj-zing the Hydrolytic Cleavage of the Phosphoryl Groujjs of 



Mononucleotides 590 



1. Phosphatases of Low Degrees of Specificitj- 590 



2. Specific Nucleotide Phosphatases (Nucleotidases) 591 



a. 5'-Nucleotidases 591 



b. 3'-Nucleotidase 592 



3. Phosphatases as Phosphotransferases Between Phosphoric Acid Esters 

 and Nucleosides 593 



IV. Nucleoside Kinases 594 



V. Enzj'mes Acting on the Amino Groups of Purine and Pyrimidir.e Com- 

 pounds 595 



1. Enzymic Deamination of the Adenine Group 595 



a. Behavior of Free Adenine 595 



b. Adenyl Deaminase of Aspergillvs oryzae 596 



c. Adenosine Deaminase 596 



d. 5' -Adenylic Acid Deaminase 597 



2. Enzymic Deamination of the Guanine Group: Guanase, Guanosine 

 Deaminase, Guanylic Acid Deaminase 598 



3. Enzymes Deaminating the Cytosine Group 599 



4. Evidence for Transamination in the Purine and the Pyrimidine Field . . 599 

 VI. Enz.ymes Acting on the Linkages Between the l^asic and the Carbohydrate 



Groups of Nucleic Acid Derivatives 600 



] . Nucleoside Phosphorylases 602 



a. Purine Nucleoside Phosphorylases 602 



(1) Animal Enzymes 602 



(2) Enzymes of Microorganisms 603 



b. Pj'rimidine Nucleoside Phosphorylases 604 



555 



