Molecular cloning, expression, and functional analysis of copper amine oxidase gene from mulberry (Morus alba L.)

Molecular cloning, expression, and functional analyses of plasmanylethanolamine desaturase gene of Takifugu rubripes

The aging population has led to a significant increase in neurodegenerative diseases, particularly Alzheimer's disease (AD), which adversely affects the quality of life and longevity of the elderly. Abnormal plasmalogen metabolism plays a crucial role in the pathogenesis of AD. This study focused on tmem189, a key gene involved in plasmalogen synthesis. We successfully cloned and characterized the open reading frame (ORF) of tmem189 in Takifugu rubripes, revealing that it encodes a protein consisting of 275 amino acids. Notably, tmem189 expression was found to be higher in brain compared to other tissues. We transfected a GFP-tagged eukaryotic expression vector into 293 T cells, confirming successful expression of tmem189 with increased expression  levels. Additionally, liquid chromatography-mass spectrometry (LC-MS) analysis demonstrated that tmem189 promotes plasmalogen synthesis in the transfected 293T cells. Our findings suggest that tmem189 could serve as a potential target for the treatment of neurodegenerative diseases, providing new insights into the promotion of plasmalogen synthesis.

Mining and characterization of a novel cytochrome P450 MaCYP71BG22 involved in the C4-stereoselective hydroxylation of 1-deoxynojirimycin biosynthesis in mulberry leaves

1-Deoxynojirimycin (DNJ), a primary active component in mulberry leaves, has garnered significant attention due to its unique structure and notable pharmacological properties. Our previous investigations have elucidated the biosynthetic pathways of DNJ from lysine to 2-methylpiperidine. However, the hydroxylation process and its underlying mechanisms remain elusive. In this study, five CYP450s hydroxylase genes significantly correlated (P < 0.05) with DNJ content in mulberry leaves at various time were screened through transcriptome profile. MaCYP71BG22 was first cloned and functionally characterized. This gene was shown to specifically catalyze the stereoselective hydroxylation of (R)-2-methylpiperidine at the C4-position to produce (2R, 4R)-2-methylpiperidin-4-ol. In hairy roots of mulberry, overexpression of MaCYP71BG22 increased DNJ accumulation, while virus-induced gene silencing (VIGS) decreased its production. Furthermore, structural-function analysis pinpointed a critical residue, G460, in MaCYP71BG22, mutation of this residue to G460E enhanced the enzyme's catalytic efficiency. This study represents the first report of a CYP450 hydroxylase involved in the biosynthesis of piperidine alkaloids in mulberry leaves, and demonstrates that MaCYP71BG22 selectively catalyzes the C4-stereoselective hydroxylation of (R)-2-methylpiperidine in DNJ biosynthesis. These findings further elucidate the DNJ biosynthetic pathway and provide new insights into the stereo- and regio-selective hydroxylation abilities of CYP450s hydroxylase in DNJ biosynthesis.

Mining and functional characterization of NADPH-cytochrome P450 reductases of the DNJ biosynthetic pathway in mulberry leaves

BACKGROUND

1-Deoxynojirimycin (DNJ), the main active ingredient in mulberry leaves, with wide applications in the medicine and food industries due to its significant functions in lowering blood sugar, and lipids, and combating viral infections. Cytochrome P450 is a key enzyme for DNJ biosynthesis, its activity depends on the electron supply of NADPH-cytochrome P450 reductases (CPRs). However, the gene for MaCPRs in mulberry leaves remains unknown.

RESULTS

In this study, we successfully cloned and functionally characterized two key genes, MaCPR1 and MaCPR2, based on the transcriptional profile of mulberry leaves. The MaCPR1 gene comprised 2064 bp, with its open reading frame (ORF) encoding 687 amino acids. The MaCPR2 gene comprised 2148 bp, and its ORF encoding 715 amino acids. The phylogenetic tree indicates that MaCPR1 and MaCPR2 belong to Class I and Class II, respectively. In vitro, we found that the recombinant enzymes MaCPR2 protein could reduce cytochrome c and ferricyanide using NADPH as an electron donor, while MaCPR1 did not. In yeast, heterologous co-expression indicates that MaCPR2 delivers electrons to MaC3'H hydroxylase, a key enzyme catalyzing the production of chlorogenic acid from 3-O-p-coumaroylquinic acid.

CONCLUSIONS

These findings highlight the orchestration of hydroxylation process mediated by MaCPR2 during the biosynthesis of secondary metabolite biosynthesis in mulberry leaves. These results provided a foundational understanding for fully elucidating the DNJ biosynthetic pathway within mulberry leaves.