Bioscientific topics concerning Aspergillus oryzae
Traditional Japanese cuisine (“Washyoku” in Japanese) was added to the UNESCO’s Intangible Culture Heritage list in 2013. Over the past 1,000 years, the use of fungal hydrolytic enzymes prevailed in the Japanese fermentation industries. Almost all characteristic flavors and tastes of these traditional fermented foods are developed using the malted rice with Aspergillus oryzae (“kōji” in Japanese). In 2006, the Brewing Society of Japan certified A. oryzae, A. sojae and A. luchuensis as the national microorganisms of Japan. In this review, a novel enzymatic production of glutamate from glutamine and new Skn-1a/Pou2f3 umami taste receptors are discussed. Biological characteristics for Aspergillus, such as the AoSO protein accumulation at the septal pore, and the large non-conserved region of the tethering protein Leashin, are presented and described here, together with the analyses of α-amylase, ManR functions, S21 family glycine-D-alanine aminopeptidase (GdaA), and ionic interactions between the fungal hydrophobin RolA and cutinase CutL1. Furthermore, I discuss the development of antihypertensive peptide (GY, SY)-enriched soy-sauce-like seasoning and the bifidogenic effect of supplemental acid protease from A. oryzae.
Consumption of an acid protease derived from A. oryzae was shown to have bifidogenic effects in rats, with a considerable increase in Bifidobacterium content found in the cecum of rats fed with a high-fat diet supplemented with the A. oryzaederived Amano protease preparation. The effect cannot be explained by the activity of acid protease at the concentration of 1-g/kg of this preparation, but four-fold higher concentrations of acid protease, compared with those initially used in the diet, were found to cause a significant bifidogenic effect. Previously, aspartic acid was reported to be released following the trypsinogen activation by the trypsinogen-kinase found in A. oryzae, which was shown to be identical to the A. oryzae-derived acid-protease. In human duodenum, trypsinogen is converted to its active form, trypsin (EC 126.96.36.199), by membrane bound enteropeptidase (EC 188.8.131.52). Free trypsin then catalyzes the conversion of additional trypsinogen to trypsin and activates chmotrypsinogen, pro-carboxypeptidases, and proelastase. Acid protease (aspergillopepsin I, EC 184.108.40.206) from A. tubingensis (formerly designated as Aspergillus saitoi) activates the generation of trypsin from trypsinogen, which was shown to be associated with the cleavage of the Lys6-Ile bond and the release of hexapeptide. Previously, Asp76 of the acid protease, aspergillopepsin I, was identified as a binding site of the basic substrate, trypsinogen.
Journal of Biochemistry & Biotechnology