TAKADIASTAS ADENOSINE DEAMINASE CALF DUODENAL ADENOSINE DEAMINASE AND RABBIT MUSCLE ADENOSINE MONOPHOSPHATE DEAMINASE . A COMPARISON OF PHYSICAL PROPERTIES AND AMINO ACID COMPOSITION

Hydrodynamic properties indicate that takadiastase adenosine deaminase, now purified to apparent homogeneity, has a molecular weight of approximately 217,000. Urea reversibly denatures this enzyme, causing it to dissociate into subunits of molecular weight approximately 105,000. Calf duodenal adenosine deaminase has a molecular weight of approximately 52,000, considerably higher than previous estimates based on gel filtration. Urea denatures this enzyme irreversibly, causing an increase in frictional coefficient from 1.4 to 2.1 without change in molecular weight. Rabbit muscle adenosine monophosphate deaminase has a molecular weight of approximately 270,000, and is also denatured irreversibly in urea. Mercurials, previously found to bind to the adenosine deaminases in competition with nucleosides, produce no apparent change in hydrodynamic properties of these enzymes. Amino acid analyses are presented for each protein and indicate the presence of cysteine-half-cystine residues in numbers that are equal to the number of p- mercuribenzoate-titratable groups in both adenosine deaminases. © 1968, American Chemical Society. All rights reserved.