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Journal of Bacteriology, July 2000, p. 3644-3648, Vol. 182, No. 13
0021-9193/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.

Cyclic Guanosine-3',5'-Monophosphate and Biopteridine Biosynthesis in Nocardia sp.

Jong-Keun Son¹ and John P. N. Rosazza^2,*

College of Pharmacy, Yeungnam University, Kyongsan 712-749, Korea,¹ and Division of Medicinal and Natural Products Chemistry, College of Pharmacy, Center for Biocatalysis and Bioprocessing, University of Iowa, Iowa City, Iowa 52242²

Received 20 December 1999/Accepted 7 April 2000

Nocardia sp. strain NRRL 5646 contains a nitric oxide synthase (NOS) enzyme system capable of generating nitric oxide (NO) from arginine and arginine-containing peptides. To explain possible roles of the NOS system in this bacterium, guanylate cyclase (GC) and tetrahydrobiopterin (H₄B) biosynthetic enzymes were identified in cell extracts and in culture media. Cell extracts contained GC activity, as measured by the conversion of GTP to cyclic guanosine-3',5'-monophosphate (cGMP) at 9.56 pmol of cGMP h¹ mg of protein¹. Concentrations of extracellular cGMP in culture media were significantly increased, from average control levels of 45 pmol cGMP liter¹ to a maximum of 315 pmol liter¹, in response to additions of GTP, L-arginine, H₄B, and sodium nitroprusside to growing Nocardia cultures. On the other hand, the NOS inhibitor N^G-nitro-L-arginine and the GC inhibitor 1H-[1,2,4]oxadiazole[4,3-a]quinoxalin-1-one both dramatically decreased extracellular cGMP levels. Activities for GTP-cyclohydrase-1,6-pyruvoyltetrahydropterin synthase and sepiapterin reductase, enzymes essential for H₄B biosynthesis, were present in Nocardia culture extracts at 77.5 pmol of neopterin and 45.8 pmol of biopterin h¹ mg of protein¹, respectively. In Nocardia spp., as in mammals, GTP is a key intermediate in H₄B biosynthesis, and GTP is converted to cGMP by a GC enzyme system that is activated by NO.

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^* Corresponding author. Mailing address: Division of Medicinal and Natural Products Chemistry, College of Pharmacy, Center for Biocatalysis and Bioprocessing, University of Iowa, Iowa City, IA 52242. Phone: (319) 335-4902. Fax: (319) 335-4901. E-mail: john-rosazza{at}uiowa.edu.

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Journal of Bacteriology, July 2000, p. 3644-3648, Vol. 182, No. 13
0021-9193/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.

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