Molecular Soil Biology 2024, Vol.15, No.1, 1-7 http://bioscipublisher.com/index.php/msb 2 1 Discovery and Naming of Biotin Biotin (Vitamin B7 or Vitamin H) is a water-soluble vitamin essential for the normal metabolism of fats and proteins. In 1901, Wildiers first discovered a factor in yeast that is essential for its growth and named it "biotin". Bateman's team fed test animals an overdose of raw egg whites and found that this resulted in dermatitis and hair loss, which disappeared when the raw egg whites were heated (Bateman, 1916). Boas (1927) described an injury to the skin of rats caused by feeding them raw egg whites, and the appearance of a "protective factor X" in various foods which prevented and cured this injury. Allison's team discovered a respiratory auxin whose function was to promote the growth of rhizobial isolates and named it "auxin R" (Allison et al., 1933). At the same time, Kuhn also discovered this factor and called it Vitamin H. In 1936, Kogl and Tonnis isolated a substance in egg yolks that is essential for yeast growth and called it "biotin". In 1941, Du Vigneagud's team identified coenzyme R and biotin as the same substance, formalized the molecular formula of biotin, and isolated it from the liver (Du Vigneaud et al., 1940; György et al., 1940). The following year, Du Vigneaud's team formalized the structure of biotin (Du Vigneaud, 1942). 2 Synthesis of Biotin Bacteria and plants can synthesize the required biotin by themselves (Prasad et al., 1998; Stolz et al., 1999). The first relevant explorations of biotin synthesis were done in bacteria. Initially, the biotin synthesis pathway starting from primeloyl CoA and alanine was elucidated in bacteria. And biotin biosynthesis in bacteria involves a four-step reaction with the products being 7-keto-8-aminopelargonic acid (KAPA), 7,8-diaminopelargonic acid (DAPA), desulfotransfer biotin (DTB), and finally biotin. In Escherichia coli, these enzymes (bioF, bioA, bioD, bioB) are encoded by four genes clustered into a single manipulator whose structure and function have been elucidated in detail (Marquet et al., 2001). Research on biotin synthesis in plants began with the model plant Arabidopsis thaliana. The biotin synthesis pathway in plants is similar to that in bacteria, and the process is carried out by enzymes encoded by the BIO4, BIO1-BIO3, BIO1-BIO3, and BIO2 genes, which are homologs of the bacterial bioF, bioA, bioD, and bioB genes, respectively. The first step is catalyzed by KAPA synthase (BIO4) in the cytosol to produce KAPA. The enzyme that catalyzes the second and third steps is composed of DAPA synthase (BIO1) and DTB synthase (BIO3), a combined enzyme gene named BIO1-BIO3 (Muralla et al., 2008) that catalyzes KAPA to produce DTB in mitochondria. The final step is catalyzed by biotin synthase (BIO2) to produce biotin in mitochondria. The BIO2-catalysed step is considered to be the rate-limiting step in the biotin synthesis pathway. Unlike the biotin synthesis pathway in bacteria, biotin in plants is synthesized at two different sites. The initial synthesis product, KAPA, is synthesized in the cytosol while the final conversion of desulfated biotin to biotin occurs in the mitochondria (Weaver et al., 1996; Picciocchi et al., 2003; Arnal et al., 2006). Metabolic enzymes that require biotin as a cofactor are usually located in four different sites: chloroplasts, mitochondria, proteasomes, and cytoplasm (Che et al., 2003). In recent years, it has been shown that peroxisomes exhibit involvement in biotin biosynthesis in plants and fungi. In fungi, peroxisome protein-deficient mutants exhibit biotin deficiency (Tanabe et al., 2011). 3 Advances in Plant Biotin Synthesis Genes Since the discovery of the biotin synthesis pathway in Arabidopsis thaliana, many efforts have been devoted to the study of biotin synthesis genes. AtBIO4 encodes a KAPA synthase, and the bio4-1 mutant accumulates hydrogen peroxide in large quantities and increases the expression of several genes involved in defense against reactive oxygen species signaling. genes involved in defense against reactive oxygen species signal transduction. Studies on bio4 mutants have revealed that biotin deficiency leads to light-dependent spontaneous cell death and regulates the expression of defensive genes (Li et al., 2012). In 1998, another biotin nutrient-deficient mutant, bio2, was identified and it was experimentally demonstrated that the addition of biotin resulted in normal growth of the bio2 mutant, but the addition of desulfurized biotin did not affect the mutant, thus identifying AtBIO2 as being involved in the final step of biotin synthesis. Later studies revealed that this catalytic reaction occurs in plant mitochondria and confirmed that AtBIO2 requires
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