| Autor: |
Nathan O. Kaplan, Robert H. McKay |
| Rok vydání: |
1964 |
| Předmět: |
|
| Zdroj: |
Biochimica et Biophysica Acta (BBA) - Specialized Section on Biophysical Subjects. 79:273-283 |
| ISSN: |
0926-6577 |
| DOI: |
10.1016/0926-6577(64)90008-7 |
| Popis: |
1. 1. The protein fluorescence polarization and the quantum yield of fluorescence per mole of tryptophan has been determined for the heart (H) and muscle (M) types of lactate dehydrogenases from beef and chicken. These quantum yields are among the highest yet reported for proteins. The M types have yields than the H forms. 2. 2. The qunatum yield of fluorescence and the fluorescence polarization on binding of NADH and the reduced 3-acetylpyridine analogue (AcPyADH) of NADH were determined for each of the enzymes and reveal an increase of quatum yield on binding of NADH of 1.3–2.6, and on binding of AcPyADH of 20–30-fold. 3. 3. The absolute quantum yield of fluorescence of free AcPyADH was determined and found to be 1.1%, as compared to 3% for NADH. 4. 4. The quenching of protein fluorescence on binding of coenzyme was found to be non-linear and could not be completely quenched by bound coenzyme. From these observations it has been concluded that the coenzymes may be found closely to each other and interact only with certain tryptophan residues in the enzyme. 5. 5. A method is presented for the combined fluoremetric determination of the number of coenzyme binding sites and the coenzyme dissociation constant. For all of the enzymes, the number of binding sites was 3–4 and the coenzyme dissociation constants approx. 10 −7 M. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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