title: Structure and characterization of human carboxylesterase 1A1, 1A2, and 1A3 genes.
abstract: OBJECTIVE
  Human carboxylesterase (CES) 1A1 gene (14 exons) and CES1A3 pseudogene (six exons) are inverted and duplicated genes in a reference sequence (NT_010498). In contrast, earlier studies reported the CES1A2 gene (14 exons) instead of the CES1A3 pseudogene. The sequences of the CES1A2 gene downstream and upstream of intron 1 are identical with those of the CES1A1 and CES1A3 genes, respectively. A CES1A1 variant of which exon 1 is converted with that of the CES1A3 gene (the transcript is CES1A2) has recently been identified. We sought to clarify the confusing gene structure of human CES1A.
  
  
  METHODS
  A panel of 55 human liver as well as 318 blood samples (104 Caucasians, 107 African-Americans, and 107 Japanese) was used to clarify the gene structures of CES1A1, CES1A2, and CES1A3. Real-time reverse transcription-PCR and western blot analysis were carried out. Imidapril hydrolase activity in human liver microsomes and cytosol was determined by liquid chromatography-mass spectrometry (LC-MS)/MS.
  
  
  RESULTS
  By PCR analyses, we found that the CES1A2 gene is a variant of the CES1A3 gene. Four haplotypes, A (CES1A1 wild type and CES1A3), B (CES1A1 wild type and CES1A2), C (CES1A1 variant and CES1A3), and D (CES1A1 variant and CES1A2), were demonstrated. Ethnic differences were observed in allele frequencies of CES1A1 variant (17.3% in Caucasians and African-Americans and 25.2% in Japanese) and CES1A2 gene (14.4% in Caucasians, 5.1% in African-Americans, and 31.3% in Japanese). In human livers whose diplotype was A/A and C/C or C/D, no CES1A2 and CES1A1 mRNA was detected, respectively. In the other participants, the CES1A1 mRNA levels were higher than the CES1A2 mRNA levels. The CES1A proteins translated from CES1A1 mRNA and CES1A2 mRNA were detected in both human liver microsomes and cytosol fractions suggesting that the differences in exon 1 encoding a signal peptide did not affect the subcellular localization. Imidapril hydrolase activities reflected the CES1A protein levels.
  
  
  CONCLUSIONS
  We found that the CES1A2 gene is a variant of the CES1A3 pseudogene. The findings presented here significantly increase our understanding about the gene structure and expression properties of human CES1A.
authors.affiliation: Drug Metabolism and Toxicology, Division of Pharmaceutical Sciences, Graduate School of Medical Science, Kanazawa University, Kakuma-machi, Kanazawa, Japan.
authors.forename: Tatsuki
authors.initials: T
authors.lastname: Fukami
authors.forename: Miki
authors.initials: M
authors.lastname: Nakajima
authors.forename: Taiga
authors.initials: T
authors.lastname: Maruichi
authors.forename: Shiori
authors.initials: S
authors.lastname: Takahashi
authors.forename: Masataka
authors.initials: M
authors.lastname: Takamiya
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Aoki
authors.forename: Howard L
authors.initials: HL
authors.lastname: McLeod
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Yokoi
mesh_terms: D000483:Alleles; D000959:Antihypertensive Agents / Q000494:pharmacology; D043182:Carboxylesterase / Q000235:genetics*; D005091:Exons; D005786:Gene Expression Regulation; D005787:Gene Frequency; D006239:Haplotypes; D006801:Humans; D048289:Imidazolidines / Q000494:pharmacology; D007438:Introns; D008099:Liver / Q000378:metabolism; D013058:Mass Spectrometry / Q000379:methods; D008862:Microsomes, Liver / Q000378:metabolism; D002265:Carboxylic Ester Hydrolases
chemical_list: D000959:Antihypertensive Agents; D043182:Carboxylesterase; D048289:Imidazolidines; C065166:imidapril; C474609:CES1 protein, human; D002265:Carboxylic Ester Hydrolases