Two different hepatic adenosine deaminases in the chicken

Ma, Pujades; Fisher, James R.

doi:10.1016/0005-2744(68)90253-2

Cited by 57 publications

(17 citation statements)

References 19 publications

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“…4.4) is an important enzyme [1] of the purine metabolism which catalyses the irreversible deamination of adenosine and 2 0 -deoxyadenosine to inosine and 2 0 -deoxyinosine, respectively (scheme 1). This enzyme has been found in plants, bacteria [2], invertebrates [3], vertebrates [4] and mammals [5,6], including humans [7 -9]. ADA is present in many human tissues, but the highest levels have been found in lymph nodes, spleen and thymus [1].…”

Section: Introductionmentioning

confidence: 99%

A study on the inhibition of adenosine deaminase

Alunni

Orrù

Ottavi

2008

Journal of Enzyme Inhibition and Medicinal Chemistry

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Adenosine deaminase (ADA, EC 3.5.4.4) catalyses the irreversible deamination of adenosine and 2 0 -deoxyadenosine to inosine and 2 0 -deoxyinosine, respectively. In this study the inhibition of ADA from bovine spleen by several molecules with structure related to that of the substrate or product has been quantified. The inhibitors adenine, purine, inosine, 2-aminopurine, 4-aminopyrimidine, 4-aminopyridine, 4-hydroxypyridine and phenylhydrazine are shown to be competitive inhibitors with K I (mM) values of 0.17, 1.1, 0.35, 0.33, 1.3, 1.8, 1.4 and 0.25, respectively. Synergistic inhibition by various combinations of molecules that imitate the structure of the substrate has never been observed. Some general conclusions are: i) the enzyme ADA from bovine spleen we have used is appropriate for kinetic studies of inhibition and mechanistic studies; it can be a reference catalytic system for the homogeneous comparison of various inhibitors; ii) this enzyme presents very rigid requirements for binding the substrate: variations in the structure of adenosine imply the loss of important interactions.

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Section: Introductionmentioning

confidence: 99%

A study on the inhibition of adenosine deaminase

Alunni

Orrù

Ottavi

2008

Journal of Enzyme Inhibition and Medicinal Chemistry

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“…Adenosine deaminase was prepared by modifica tion of the method of Ma and Fisher [1] from livers of freshly killed 12-week-old FP-strain chickens. A 40-60% ammonium sulfate precipitate of liver homoge nate was applied in a total volume of 2 ml to a Sepha cryl S-200 column (2.5 X 100 cm), eluted at a flow rate of 26 ml/h with 0.05 mol/1 sodium phosphate buffer.…”

Section: Enzyme Preparation and Column Chromatographymentioning

confidence: 99%

“…The 35,000-and 280,000-dalton ADA isozymes account for virtually all the ADA activity in most mammalian species. In some species, such as aves, the 280,000-dalton isozyme is not seen [1], The two mammalian isozymes ADAi and ADAi +cp, which share the same catalytic unit, do not differ significantly in their kinetic properties.…”

Section: Introductionmentioning

confidence: 99%

“…Thus, avian liver contains, in equal amounts, two ADA isozymes with molecular weights of approximately 100,000 and 35,000 daltons [1], The 100,000-dalton ADA2 iso zyme differs from the 35,000-dalton ADAi isozyme not only in molecular weight, but in kinetic properties. Thus ADA2 has a higher K for adenosine and a lower relative ability to deaminate deoxyadenosine than ADAi.…”

Section: Introductionmentioning

confidence: 99%

“…In contrast, in many lower vertebrates, an additional, kinetically different, ADA iso zyme of 100,000 daltons (ADA2) emerges as a maj or component of total ADA activity [1,[21][22][23]. Thus, avian liver contains, in equal amounts, two ADA isozymes with molecular weights of approximately 100,000 and 35,000 daltons [1], The 100,000-dalton ADA2 iso zyme differs from the 35,000-dalton ADAi isozyme not only in molecular weight, but in kinetic properties.…”

Section: Introductionmentioning

confidence: 99%

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Comparison and Possible Homology of Isozymes of Adenosine Deaminase in Aves and Humans

Ratech

Thorbecke

Meredith

et al. 1981

Enzyme

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Two kinetically distinct adenosine deaminase (ADA) isozymes with different molecular weights (35,000 and 100,000 daltons) are found in chicken liver in approximately equal amounts. The 100,000-dalton ADA has a markedly higher K(m) for adenosine and a markedly lower deaminating activity for deoxyadenosine relative to adenosine than does the 35,000-dalton ADA. A 100,000-dalton ADA isozyme has only recently been detected in mammalian tissues, where, in contrast to the chicken, it is only a trace component of total ADA activity. The human 100,000-dalton ADA isozyme, compared to the human 35,000- dalton ADA isozyme, has been reported to have a higher K(m), a lower pH optimum, and a greater resistance to inhibition by erythro-9-(2-hydroxy-2-nonyl) adenine (EHNA). The similarity in K(m)s of the 100,000-dalton ADA isozyme in man and aves led us to hypothesize that these isozymes might be descended from a common ancestor and therefore also be similar as to other kinetic parameters. We now report that the chicken 100,000-dalton ADA, like the human 100,000-dalton isozyme, has a lower pH optimum and a greater resistance to inhibition by EHNA than does the avian or human 35,000-dalton isozyme. In addition, the avian 100,000-dalton isozyme is relatively resistant to inhibition by deoxycoformycin and has a cathodal rather than an anodal electrophoretic mobility at pH 6.5. Conversely, we report that the human 100,000-dalton ADA isozyme, similar to the avian 100,000-dalton ADA, has markedly lower relative deaminating activity for deoxyadenosine than does the 35.000- dalton ADA human isozyme. Thus, despite the marked difference in the relative amounts of the 100,000- and 35,000-dalton ADA isozymes in man as compared to aves, the 100.000- dalton ADA isozymes from both species exhibit several similar kinetic properties, all of which are different from those of the 35,000-dalton ADA isozymes. We also report using a new sensitive assay, relative rates of degradation by the two chicken isozymes of several naturally occurring modified adenine nucleosides which are inhibitory to in vitro human lymphocyte proliferation.

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