Covalently bound phosphate residues in bovine milk xanthine oxidase and in glucose oxidase from Aspergillus niger: A reevaluation

Journal Article · Fri Sep 01 04:00:00 EDT 1989 · Proceedings of the National Academy of Sciences of the United States of America; (USA)

DOI:https://doi.org/10.1073/pnas.86.17.6493· OSTI ID:7194912

Johnson, J L; Rajagopalan, K V ^[1]; London, R E ^[2]

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1. Duke Univ. Medical Center, Durham, NC (USA)
2. National Institute of Environmental Health Science, Research Triangle Park, NC (USA)

The reported presence of covalently bound phosphate residues in flavoproteins has significant implications with regard to the catalytic mechanisms and structural stability of the specific enzymes themselves and in terms of general cellular metabolic regulation. These considerations have led to a reevaluation of the presence of covalently bound phosphorus in the flavoproteins xanthine oxidase and glucose oxidase. Milk xanthine oxidase purified by a procedure that includes anion-exchange chromatography is shown to contain three phosphate residues. All three are noncovalently associated with the protein, two with the FAD cofactor, and one with the molybdenum cofactor. Results of chemical analysis and {sup 31}P NMR spectroscopy indicate that enzyme purified by this method contains no phosphoserine residues. Xanthine oxidase preparations purified by chromatography on calcium phosphate gel in place of DEAE-Sephadex yielded higher phosphate-to-protein ratios, which could be reduced to the expected values by additional purification on a folate affinity column. Highly active, highly purified preparations of glucose oxidase are shown to contain only the two phosphate residues of the FAD cofactor. The covalently bound bridging phosphate reported by others may arise in aged or degraded preparations of the enzyme but appears not to be a constituent of functional glucose oxidase. These results suggest that the presence of covalent phosphate residues in other flavoproteins should be rigorously reevaluated as well.

• OSTI ID: 7194912
• Journal Information: Proceedings of the National Academy of Sciences of the United States of America; (USA), Journal Name: Proceedings of the National Academy of Sciences of the United States of America; (USA) Vol. 86:17; ISSN 0027-8424; ISSN PNASA
• Country of Publication: United States
• Language: English

Related Subjects

550601* -- Medicine-- Unsealed Radionuclides in Diagnostics
62 RADIOLOGY AND NUCLEAR MEDICINE
ABSORPTION SPECTROSCOPY
ANIMALS
AROMATICS
ASPERGILLUS
AZAARENES
BIOCHEMISTRY
BIOLOGICAL MATERIALS
BODY FLUIDS
CATTLE
CHEMICAL BONDS
CHEMISTRY
CHROMATOGRAPHY
COENZYMES
DOMESTIC ANIMALS
ENZYMES
EUMYCOTA
FOOD
FUNGI
HEMIACETAL DEHYDROGENASES
HETEROCYCLIC COMPOUNDS
ION EXCHANGE CHROMATOGRAPHY
ISOTOPES
LIGHT NUCLEI
MAGNETIC RESONANCE
MAMMALS
MATERIALS
METALLOPROTEINS
MILK
MOLECULAR STRUCTURE
MOLYBDENUM COMPOUNDS
NUCLEAR MAGNETIC RESONANCE
NUCLEI
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
OXIDOREDUCTASES
OXYGEN COMPOUNDS
PHOSPHATES
PHOSPHORUS 31
PHOSPHORUS COMPOUNDS
PHOSPHORUS ISOTOPES
PLANTS
PROTEINS
PURINES
REFRACTORY METAL COMPOUNDS
RESONANCE
RUMINANTS
SEPARATION PROCESSES
SPECTROSCOPY
STABLE ISOTOPES
TRANSITION ELEMENT COMPOUNDS
VERTEBRATES
XANTHINES