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Regulation, purification, and properties of xanthine dehydrogenase in Neurospora crassa.
J Biol Chem. 1978 Apr 25; 253(8):2604-14.JB

Abstract

Xanthine dehydrogenase (EC 1.2.1.37) is the first enzyme in the degradative pathway by which fungi convert purines to ammonia. In vivo, the activity is induced 6-fold by growth in uric acid. Hypoxanthine, xanthine, adenine, or guanine also induce enzyme activity but to a lesser degree. Immunoelectrophoresis using monospecific antibodies prepared against Neurospora crassa xanthine dehydrogenase shows that the induced increase in enzyme activity results from increased numbers of xanthine dehydrogenase molecules, presumably arising from de novo enzyme synthesis. Xanthine dehydrogenase has been purified to homogeneity by conventional methods followed by immunoabsorption to monospecific antibodies coupled to Sepharose 6B. Electrophoresis of purified xanthine dehydrogenase reveals a single protein band which also exhibits enzyme activity. The average specific activity of purified enzyme is 140 nmol of isoxanthopterine produced/min/mg. Xanthine dehydrogenase activity is substrate-inhibited by xanthine (0.14 mM), hypoxanthine (0.3 mM), and pterine (10 micron), is only slightly affected by metal binding agents such as KCN (6 mM), but is strongly inhibited by sulfhydryl reagents such as p-hydroxymercuribenzoate (2 micron). The molecular weight of xanthine dehydrogenase is 357,000 as calculated from a sedimentation coefficient of 11.8 S and a Stokes radius of 6.37 nm. Sodium dodecyl sulfate-gel electrophoresis of the enzyme reveals a single protein band having a molecular weight of 155,000. So the xanthine dehydrogenase protein appears to be a dimer. In contrast to xanthine dehydrogenases from animal sources which typically possess as prosthetic groups 2 FAD molecules, 2 molybdenum atoms, 8 atoms of iron, and 8 acid-labile sulfides, the Neurospora enzyme contains 2 FAD molecules, 1 molybdenum atom, 12 atoms of iron, and 14 eq of labile sulfide/molecule. The absorption spectrum of the enzyme shows maxima between 400 and 500 nm typical of a non-heme iron-containing flavoprotein.

Authors

No affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, U.S. Gov't, P.H.S.

Language

eng

PubMed ID

147274

Citation

Lyon, E S., and R H. Garrett. "Regulation, Purification, and Properties of Xanthine Dehydrogenase in Neurospora Crassa." The Journal of Biological Chemistry, vol. 253, no. 8, 1978, pp. 2604-14.
Lyon ES, Garrett RH. Regulation, purification, and properties of xanthine dehydrogenase in Neurospora crassa. J Biol Chem. 1978;253(8):2604-14.
Lyon, E. S., & Garrett, R. H. (1978). Regulation, purification, and properties of xanthine dehydrogenase in Neurospora crassa. The Journal of Biological Chemistry, 253(8), 2604-14.
Lyon ES, Garrett RH. Regulation, Purification, and Properties of Xanthine Dehydrogenase in Neurospora Crassa. J Biol Chem. 1978 Apr 25;253(8):2604-14. PubMed PMID: 147274.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Regulation, purification, and properties of xanthine dehydrogenase in Neurospora crassa. AU - Lyon,E S, AU - Garrett,R H, PY - 1978/4/25/pubmed PY - 1978/4/25/medline PY - 1978/4/25/entrez SP - 2604 EP - 14 JF - The Journal of biological chemistry JO - J Biol Chem VL - 253 IS - 8 N2 - Xanthine dehydrogenase (EC 1.2.1.37) is the first enzyme in the degradative pathway by which fungi convert purines to ammonia. In vivo, the activity is induced 6-fold by growth in uric acid. Hypoxanthine, xanthine, adenine, or guanine also induce enzyme activity but to a lesser degree. Immunoelectrophoresis using monospecific antibodies prepared against Neurospora crassa xanthine dehydrogenase shows that the induced increase in enzyme activity results from increased numbers of xanthine dehydrogenase molecules, presumably arising from de novo enzyme synthesis. Xanthine dehydrogenase has been purified to homogeneity by conventional methods followed by immunoabsorption to monospecific antibodies coupled to Sepharose 6B. Electrophoresis of purified xanthine dehydrogenase reveals a single protein band which also exhibits enzyme activity. The average specific activity of purified enzyme is 140 nmol of isoxanthopterine produced/min/mg. Xanthine dehydrogenase activity is substrate-inhibited by xanthine (0.14 mM), hypoxanthine (0.3 mM), and pterine (10 micron), is only slightly affected by metal binding agents such as KCN (6 mM), but is strongly inhibited by sulfhydryl reagents such as p-hydroxymercuribenzoate (2 micron). The molecular weight of xanthine dehydrogenase is 357,000 as calculated from a sedimentation coefficient of 11.8 S and a Stokes radius of 6.37 nm. Sodium dodecyl sulfate-gel electrophoresis of the enzyme reveals a single protein band having a molecular weight of 155,000. So the xanthine dehydrogenase protein appears to be a dimer. In contrast to xanthine dehydrogenases from animal sources which typically possess as prosthetic groups 2 FAD molecules, 2 molybdenum atoms, 8 atoms of iron, and 8 acid-labile sulfides, the Neurospora enzyme contains 2 FAD molecules, 1 molybdenum atom, 12 atoms of iron, and 14 eq of labile sulfide/molecule. The absorption spectrum of the enzyme shows maxima between 400 and 500 nm typical of a non-heme iron-containing flavoprotein. SN - 0021-9258 UR - https://www.unboundmedicine.com/medline/citation/147274/Regulation_purification_and_properties_of_xanthine_dehydrogenase_in_Neurospora_crassa_ L2 - https://linkinghub.elsevier.com/retrieve/pii/S0021-9258(17)40864-7 DB - PRIME DP - Unbound Medicine ER -