Infrared spectroscopic study of a phosphoryl-containing enzyme: cytosolic aspartate aminotransferase
A Fourier Transform Infrared spectroscopic study of cytosolic aspartate aminotransferase has been carried out in order to determine the ionization state of the phosphate group of the bound pyridoxal phosphate. The band arising from the symmetric stretching of the dianionic phosphate monoester has been identified in holoenzyme spectra in solution. Its integrated intensity does not change with pH in the range 5.3-8.6, the value being close to the integrated intensity of the same band in free pyridoxal phosphate in solution at pH 8-9. On the other hand, for free cofactor, the integrated intensity changes with pH according to the pK expected for a 5'-phosphate group in solution. It appears, therefore, that the 5'-phosphate group of the bound cofactor remains mostly dianionic in the pH range 5.3-8.6, and a small /sup 31/P-NMR chemiCal shift/pH titration dependent curve observed in holoenzyme solutions seems due to the phosphate group in the protein, likely the Lys 258-pyridoxal phosphate Schiff's base. These results also show Fourier Transform Infrared Spectroscopy as a valuable technique in the study of phosphoryl-containing proteins.
- Research Organization:
- Virginia Commonwealth Univ., Richmond
- OSTI ID:
- 5020361
- Report Number(s):
- CONF-8606151-; TRN: 86-034824
- Journal Information:
- Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States), Vol. 45:6; Conference: 76. annual meeting of the Federation of American Society for Experimental Biology, Washington, DC, USA, 8 Jun 1986
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
62 RADIOLOGY AND NUCLEAR MEDICINE
AMINOTRANSFERASES
INFRARED SPECTRA
MOLECULAR STRUCTURE
CHEMICAL SHIFT
NMR SPECTRA
NUCLEAR MAGNETIC RESONANCE
PH VALUE
PHOSPHORUS 31
SCHIFF BASES
ENZYMES
IMINES
ISOTOPES
LIGHT NUCLEI
MAGNETIC RESONANCE
NITROGEN TRANSFERASES
NUCLEI
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PHOSPHORUS ISOTOPES
RESONANCE
SPECTRA
STABLE ISOTOPES
TRANSFERASES
550201* - Biochemistry- Tracer Techniques
550600 - Medicine