Adenosine deaminase isoenzymes of the opossum Didelphis virginiana: initial chromatographic and kinetic studies.
Extracts of liver and spleen were used to isolate opossum adenosine deaminase isoenzymes (ADA1 and ADA2) and to determine their activities with adenosine and 2'-deoxyadenosine as substrates. Km values (microM) for adenosine and 2'-deoxyadenosine, respectively, as substrates for partially purified opossum liver adenosine deaminase isoenzymes were ADA1: 57 +/- 7 vs. 26 +/- 4 and ADA2: 285 +/- 25 vs. 580 +/- 92. In crude spleen extract, ADA2 activity was stable at 56 degrees C during 40 min of incubation. ADA1 activity declined in a linear fashion under the above conditions with an apparent T1/2 of 80 min. Sephadex G-150 column chromatography of crude spleen extract showed the apparent molecular weight of the ADA activity not inhibited by (+/-)-EHNA (i.e. ADA2) to be 170 kDa; ADA activity fully inhibited by (+/-)-EHNA (i.e. ADA1) eluted in the fractions corresponding to a molecular weight of 35 kDa.
Niedzwicki
J G
JG
Oncology Center, North Dartmouth, MA 02747, USA.
Liou
C
C
Abernethy
D R
DR
Lima
J E
JE
Hoyt
A
A
Lieberman
M
M
Bethlenfalvay
N C
NC
D000243:Adenosine Deaminase / Q000737:chemistry* / Q000302:isolation & purification; D000818:Animals; D004795:Enzyme Stability; D006801:Humans; D007527:Isoenzymes / Q000737:chemistry* / Q000302:isolation & purification; D007700:Kinetics; D008099:Liver / Q000201:enzymology; D009893:Opossums / Q000378:metabolism*; D013154:Spleen / Q000201:enzymology
D007527:Isoenzymes; D000243:Adenosine Deaminase