Efficient Synthesis of High-Active Myoglobin and Hemoglobin by Reconstructing the Mitochondrial Heme Synthetic Pathway in Engineered Saccharomyces cerevisiae

Currently, various types of myoglobins and hemoglobins are widely used in the fields of food additives and biocatalytic applications. However, the limited availability of heme constrains the biosynthesis of these high-activity hemoproteins in microbial chassis cells. In this work, a new heme synthetic pathway was reconstructed in the mitochondria by eliminating the spatial barrier during heme synthesis in Saccharomyces cerevisiae, resulting in a significant enhancement in intracellular heme supply. To further enhance the supply of the essential precursor for heme synthesis (5-aminolevulinate, ALA), the special ALA exporter in the mitochondrial membrane (Ort1p) was identified and knocked out. Moreover, the mitochondrial heme exporter (Ygr127wp) was overexpressed to promote the transport of heme to the cytoplasm to participate in the synthesis of various myoglobins and hemoglobins. Based on these strategies in the engineered strain, the binding ratios of heme in porcine myoglobin (52.4 ± 4.9%) and soybean hemoglobin (75.5 ± 2.8%) were, respectively, increased by 2.4-fold and 3.6-fold, and the titers of porcine myoglobin (130.5 ± 2.8 mg·L−1) and soybean hemoglobin (152.8 ± 2.6 mg·L−1), respectively, increased by 31.1% and 42.1%. Furthermore, the engineered strain presents great potential in the efficient synthesis of other heme-binding proteins and enzymes in S. cerevisiae.