ABSTRACT
Multi-omics analyses was performed to compare the conditions of adding Tyr and Cystine in CHO cells. The addition of cystine resulted in decreased viability and productivity owing to endoplasmic reticulum (ER) stress and the promotion of ER-associated degradation (ERAD) and apoptosis. In contrast, addition of Tyr suppressed ER stress and apoptosis. This effect could be due to the increase in ubiquinone (Coenzyme Q10) biosynthesized from Tyr. To inhibit apoptosis caused by cystine addition, Tyr was added simultaneously with cystine, which improved growth, viability, and mAb productivity owing to the activation of GSH metabolism, suppression of ER stress and oxidative stress, reduction of ERAD, and activation of the tricarboxylic acid cycle.
Subject(s)
Cystine , Tyrosine , Cricetinae , Animals , Cricetulus , CHO Cells , Oxidative StressABSTRACT
Trichoderma reesei cellobiohydrolase I (TrCel7A) is a molecular motor that directly hydrolyzes crystalline celluloses into water-soluble cellobioses. It has recently drawn attention as a tool that could be used to convert cellulosic materials into biofuel. However, detailed mechanisms of action, including elementary reaction steps such as binding, processive hydrolysis, and dissociation, have not been thoroughly explored because of the inherent challenges associated with monitoring reactions occurring at the solid/liquid interface. The crystalline cellulose Iα and IIII were previously reported as substrates with different crystalline forms and different susceptibilities to hydrolysis by TrCel7A. In this study, we observed that different susceptibilities of cellulose Iα and IIII are highly dependent on enzyme concentration, and at nanomolar enzyme concentration, TrCel7A shows similar rates of hydrolysis against cellulose Iα and IIII. Using single-molecule fluorescence microscopy and high speed atomic force microscopy, we also determined kinetic constants of the elementary reaction steps for TrCel7A against cellulose Iα and IIII. These measurements were performed at picomolar enzyme concentration in which density of TrCel7A on crystalline cellulose was very low. Under this condition, TrCel7A displayed similar binding and dissociation rate constants for cellulose Iα and IIII and similar fractions of productive binding on cellulose Iα and IIII. Furthermore, once productively bound, TrCel7A processively hydrolyzes and moves along cellulose Iα and IIII with similar translational rates. With structural models of cellulose Iα and IIII, we propose that different susceptibilities at high TrCel7A concentration arise from surface properties of substrate, including ratio of hydrophobic surface and number of available lanes.
