Characterization of human brain nicotinamide 5′-mononucleotide adenylyltransferase-2 and expression in human pancreas

Joel A. Yalowitz, Suhong Xiao, Mangatt P. Biju, Asok Antony, Oscar Cummings, Mark A. Deeg, Hiremagalur N. Jayaram

Research output: Contribution to journalArticle

38 Citations (Scopus)

Abstract

NMNAT (nicotinamide 5′-mononucleotide adenylyltransferase; EC 2.7.7.1) catalyses the transfer of the adenylyl group from ATP to NMN to form NAD. We have cloned a novel human NMNAT cDNA, designated hNMNAT-2, from human brain. The cDNA contains a 924 bp open reading frame that encodes a 307 amino acid peptide that was expressed as a histidine-patch-containing thioredoxin fusion protein. Expressed hNMNAT-2 shared only 35 % amino acid sequence homology with the human NMNAT enzyme (hNMNAT-1), but possessed enzymic activity comparable with hNMNAT-1. Using human genomic databases, hNMNAT-2 was localized to chromosome 1q25 within a 171 kb gene, whereas hNMNAT-1 is on chromosome 1p32-35. Northern blot analysis revealed highly restricted expression of hNMNAT-2 to brain, heart and muscle tissues, which contrasts with the wide tissue expression of hNMNAT-1; different regions of the brain exhibited differential expression of hNMNAT-2. Substitution mutations of either of two invariant residues, His-24 or Trp-92, abolished enzyme activity. Anti-peptide antibody to a unique epitope within hNMNAT-2 was produced, and immunohistochemical analysis of sections of normal adult human pancreas revealed that hNMNAT-2 protein was markedly expressed in the islets of Langerhans. However, the pancreatic exocrine cells exhibited weak expression of hNMNAT-2 protein. Sections of pancreas from insulinoma patients showed strong expression of hNMNAT-2 protein in the insulin-producing tumour cells, whereas acinar cells exhibited relatively low expression of hNMNAT-2 protein. These data suggest that the unique tissue-expression patterns of hNMNAT-2 reflect distinct functions for the isoforms in the regulation of NAD metabolism.

Original languageEnglish
Pages (from-to)317-326
Number of pages10
JournalBiochemical Journal
Volume377
Issue number2
DOIs
StatePublished - Jan 15 2004

Fingerprint

Niacinamide
Pancreas
Brain
Tissue
Chromosomes
Proteins
NAD
Nicotinamide-Nucleotide Adenylyltransferase
Complementary DNA
Amino Acids
Amino Acid Sequence Homology
Peptides
Insulinoma
Thioredoxins
Acinar Cells
Enzyme activity
Enzymes
Islets of Langerhans
Histidine
Metabolism

Keywords

  • Enzyme kinetics
  • Human NMN adenylyltransferase
  • Immunohistochemistry
  • NAD metabolism
  • Protein expression
  • Protein purification

ASJC Scopus subject areas

  • Biochemistry

Cite this

Characterization of human brain nicotinamide 5′-mononucleotide adenylyltransferase-2 and expression in human pancreas. / Yalowitz, Joel A.; Xiao, Suhong; Biju, Mangatt P.; Antony, Asok; Cummings, Oscar; Deeg, Mark A.; Jayaram, Hiremagalur N.

In: Biochemical Journal, Vol. 377, No. 2, 15.01.2004, p. 317-326.

Research output: Contribution to journalArticle

Yalowitz, Joel A. ; Xiao, Suhong ; Biju, Mangatt P. ; Antony, Asok ; Cummings, Oscar ; Deeg, Mark A. ; Jayaram, Hiremagalur N. / Characterization of human brain nicotinamide 5′-mononucleotide adenylyltransferase-2 and expression in human pancreas. In: Biochemical Journal. 2004 ; Vol. 377, No. 2. pp. 317-326.
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