title: Enzymatic conversion of retinaldehyde to retinoic acid by cloned murine cytosolic and mitochondrial aldehyde dehydrogenases.
abstract: It has previously been reported that retinaldehyde can be converted to retinoic acid by cytosolic aldehyde dehydrogenase (AHD-2) in liver extracts [Biochem. Pharmacol. 42: 1279-1285 (1991)]. To determine which enzyme(s) carried out this reaction in murine embryonic stem cells, two aldehyde dehydrogenases were cloned; the AHD-2 gene was cloned from a liver cDNA library, and a closely related gene, AHD-M1, was cloned from an embryonic F9 cell cDNA library by conserved oligonucleotide sequence screening. AHD-M1 contained an open reading frame of 1554 base pairs, which encoded 517 amino acids. The AHD-M1 gene encoded a protein with a putative amino acid sequence that was 94% and 97% identical to the mitochondrial aldehyde dehydrogenases of human and rat, respectively, and thus we have cloned the murine cDNA for this enzyme for the first time. The AHD-M1 cDNA was only 64% identical to AHD-2. Northern analysis showed that AHD-M1 mRNA was constitutively expressed in F9 and P19 embryonic teratocarcinoma stem cells and in AB1 embryonic stem cells. There was a 3-5-fold retinoic acid-associated increase in the amount of this mRNA during the differentiation of F9 cells into parietal endoderm. In contrast, we could not detect the expression of AHD-2 mRNA in AB1, P19, or F9 cells, even though the F9 cells could convert retinaldehyde to retinoic acid. When the AHD-M1 and AHD-2 cDNAs were inserted into the expression vector pSG5 and transfected into cultured COS cells, 3-5-fold and 100-fold increases, respectively, in the conversion of [3H]retinaldehyde to [3H]retinoic acid could be detected by high performance liquid chromatographic assay. We conclude that both enzymes are capable of converting retinaldehyde to retinoic acid in intact COS cells. AHD-2 is more active than AHD-M1 in this conversion, but AHD-2 is not the enzyme responsible for this conversion in F9 embryonic stem cells.
authors.affiliation: Department of Pharmacology, Cornell University Medical College, New York, New York 10021.
authors.forename: M
authors.initials: M
authors.lastname: Chen
authors.forename: C
authors.initials: C
authors.lastname: Achkar
authors.forename: L J
authors.initials: LJ
authors.lastname: Gudas
mesh_terms: D000444:Aldehyde Dehydrogenase / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002454:Cell Differentiation; D002478:Cells, Cultured; D003001:Cloning, Molecular; D003600:Cytosol / Q000201:enzymology*; D018076:DNA, Complementary; D005822:Genetic Vectors; D051379:Mice; D008930:Mitochondria, Liver / Q000201:enzymology*; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000235:genetics; D012172:Retinaldehyde / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D014212:Tretinoin / Q000378:metabolism*; D014407:Tumor Cells, Cultured
chemical_list: D018076:DNA, Complementary; D012333:RNA, Messenger; D014212:Tretinoin; D000444:Aldehyde Dehydrogenase; D012172:Retinaldehyde