Structural and kinetic studies of human aldh7a1 and aldh9a1

The regulation and detoxification of endogenously and exogenously derived aldehydes is paramount to cellular survival due to the highly reactive nature of aldehydes as electrophiles. Human aldehyde dehydrogenases (ALDHs) are a superfamily of oxidoreductase enzymes that have critical roles in this regulation and detoxification. Misregulation of ALDH gene expression or mutations in the genes encoding for ALDHs lead to numerous disease pathologies. While extensive work has been conducted in understanding the metabolic roles and structures of these enzymes, there remains a need to further expand the structural and kinetic understanding of members of the human ALDH superfamily. This thesis aims to utilize the tools of structural biology and enzymology to expand the understanding of the ALDH superfamily.

Genome-wide identification and analysis of the aldehyde dehydrogenase gene superfamily in Chinese cabbage (Brassica rapa subsp. pekinensis)

Aldehyde dehydrogenases (ALDHs) encode a class of enzymes that dehydrooxidize aldehydes into corresponding carboxylic acids, which are involved in the growth and development of plants and in the response to various biological and abiotic stresses. In this study, we identified 27 ALDH genes in the Chinese cabbage genome and grouped them into 10 different families. Chromosomal mapping revealed that, except for one gene distributed on Scaffold, the remaining 26 genes were unevenly distributed on 10 chromosomes of Chinese cabbage. Based on a comparison of the homologous relationship between BrALDHs and ALDH genes in Arabidopsis thaliana, duplicated patterns of the ALDH gene family in Chinese cabbage were analyzed. The exon–intron structures, conserved protein motifs, and phylogenetic relationship with ALDH in six other species were also predicted and analyzed. Finally, we used available RNA-Seq data and real-time quantitative PCR to analyze the expression of ALDH genes in different tissues of Chinese cabbage including the roots, stems, leaves, flowers, and siliques. The results showed the tissue specificity and differential expression in different tissues of BrALDHs. The analysis of ALDH gene transcriptome data of Chinese cabbage under different stress conditions (cold, heat, drought, and salinity) showed that the response levels of different genes varied under different stresses, suggesting the function of some genes in these processes. Details of the ALDH gene family in Chinese cabbage has enriched studies on the ALDH gene family in plants and animals and is crucial for understanding ALDH function during plant growth and development.

ALDH2 Inhibition Potentiates High Glucose Stress-Induced Injury in Cultured Cardiomyocytes

Aldehyde dehydrogenase (ALDH) gene superfamily consists of 19 isozymes. They are present in various organs and involved in metabolizing aldehydes that are biologically generated. For instance, ALDH2, a cardiac mitochondrial ALDH isozyme, is known to detoxify 4-hydroxy-2-nonenal, a reactive aldehyde produced upon lipid peroxidation in diabetic conditions. We hypothesized that inhibition of ALDH leads to the accumulation of unmetabolized 4HNE and consequently exacerbates injury in cells subjected to high glucose stress. H9C2 cardiomyocyte cell lines were pretreated with 10 μM disulfiram (DSF), an inhibitor of ALDH2 or vehicle (DMSO) for 2 hours, and then subjected to high glucose stress {33 mM D-glucose (HG) or 33 mM D-mannitol as an osmotic control (Ctrl)} for 24 hrs. The decrease in ALDH2 activity with DSF pretreatment was higher in HG group when compared to Ctrl group. Increased 4HNE adduct formation with DSF pretreatment was higher in HG group compared to Ctrl group. Pretreatment with DSF leads to potentiated HG-induced cell death in cultured H9C2 cardiomyocytes by lowering mitochondrial membrane potential. Our results indicate that ALDH2 activity is important in preventing high glucose induced cellular dysfunction.