In this work, the mesoscale mechanics of metals, which links their microscopic physics and macroscopic mechanics, was established. For practical applications, the laws for quantitatively predicting life of cycle and time-dependent fracture behavior such as fatigue, hydrogen embrittlement, and high-temperature creep were derived using particle transport phenomena theories such as dislocation group dynamics, hydrogen diffusion, and vacancy diffusion. Furthermore, these concepts were also applied for estimating the degree of viscoelastic deterioration of blood vessel walls, which is dominated by a time-dependent mechanism, and for the diagnosis of aneurysm accompanied by the viscoelastic deterioration of the blood vessel wall. In these theories, new mechanical indexes were derived as dominant factors for predicting the life of fatigue crack growth and the time-dependent fracture of notched specimens of materials such as hydrogen embrittlement and high-temperature creep. Furthermore, as an example of a practical application, these theories were applied to estimate the degree of viscoelastic deterioration and chaotic motions of blood vessel walls, which are closely related to blood vessel diseases such as atherosclerosis and aneurysm. Moreover, new indexes to diagnose them were also proposed for clinical applications.
To address the climate change caused by anthropogenic emissions of greenhouse gases into the atmosphere, it is essential to understand and quantitatively elucidate their cycling on the Earth’s surface. This paper first presents an overview of the global cycling of three greenhouse gases, carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O), followed by a description of their variations in the atmosphere. This paper then presents the recent global budgets of these greenhouse gases estimated using two different approaches, top-down and bottom-up. Discussions on our current knowledge regarding the global cycling of the three gases are also presented.
While exploring phytotoxic metabolites from phytopathogenic fungi in the 1970s, we became interested in biosynthetic enzymes that catalyze Diels–Alder reactions involving biosynthesis of several phytotoxins that we isolated. Target enzymes were successfully characterized, and this triggered the identification of various Diels–Alderases in a recent decade. Through our Diels–Alderase project in 1990s, we recognized a highly efficient expression system of various biosynthetic genes with Aspergillus oryzae as a host. With the development of tools such as genomic data and bioinformatics analysis to identify biosynthetic gene clusters for natural products, we developed a highly reliable methodology such as hot spot knock-in to elucidate the biosynthetic pathways of representative fungal metabolites including phytotoxic substances. This methodology allows total biosynthesis of natural products and genome mining using silent biosynthetic gene clusters to obtain novel bioactive metabolites. Further applications of this technology are discussed.
Ubiquitin is a small protein used for posttranslational modification and it regulates every aspect of biological functions. Through a three-step cascade of enzymatic action, ubiquitin is conjugated to a substrate. Because ubiquitin itself can be post-translationally modified, this small protein generates various ubiquitin codes and triggers differing regulation of biological functions. For example, ubiquitin itself can be ubiquitinated, phosphorylated, acetylated, or SUMOylated. Via the type three secretion system, some bacterial effectors also modify the ubiquitin system in host cells. This review describes the general concept of the ubiquitin system as well as the fundamental functions of ubiquitin in the regulation of cellular responses during inflammation and bacterial infection.
γ-Glutamyltranspeptidase (GGT) has been widely used as a marker enzyme of hepatic and biliary diseases and relations between various diseases and its activity have been studied extensively. Nevertheless, several of its fundamental enzymatic characteristics had not been elucidated. We obtained homogeneous preparation of GGTs from bacteria, characterized them, and elucidated its physiological function that is common to mammalian cells, using GGT-deficient E. coli. Prior to GGT of all living organisms, we also identified catalytic nucleophile of E. coli GGT and revealed the post-translational processing mechanism for its maturation, and also its crystal structure was determined. The reaction intermediate was trapped and the structure-based reaction mechanism was presented. As for its application, using its transferase activity, we developed the enzymatic synthesis of various γ-glutamyl compounds that are promising in food, nutraceutical and medicinal industries. We found GGT of Bacillus subtilis is salt-tolerant and can be used as a glutaminase, which is important in food industry, to enhance umami of food, such as soy sauce and miso. We succeeded in converting bacterial GGT to glutaryl-7-aminocephalosporanic acid acylase, which is an important enzyme in cephem antibiotics production, by site-directed and random mutagenesis.