Investigations into the mechanism of orotidine 5'-monophosphate decarboxylase: Sources of substrate destabilization and transition state stabilization

Orotidine 5′-monophosphate decarboxylase (OMPDC) achieves a rarely paralleled rate acceleration, yet the catalytic basis prompting this enhancement have yet to be fully elucidated. To accomplish decarboxylation, OMPDC must overcome the high energy barrier due to the localized anionic charge of the intermediate. Mechanistic studies employing enzyme mutagenesis and product or intermediate analogues were used to investigate possible transition state stabilization by a carbene resonance structure. Viability of the carbene structure depends upon a key hydrogen bond between O4 of the substrate and the amide backbone of a conserved serine or threonine. Substitution of the conserved residue with Pro resulted in a kcat/KM of 1 M-1s-1; deletion of the FUMP O4 resulted in a product analogue that does not undergo H6 exchange or inhibit decarboxylation. Hence, indirect evidence reveals the O4-backbone interaction plays an important role for binding and catalysis. OMPDC likely has honed multiple mechanisms to attain its remarkable catalysis. The successful crystallizations of OMPDC a decade ago sparked hypotheses that structure and sequence conserved residues induced productive strain on the substrate-enzyme complex. Here, we demonstrate a new source of stress: a hydrophobic pocket adjacent to the OMP carboxylate that exhibits kinetic parameters characteristic of substrate destabilization. Substitution of these residues with hydrophilic side-chains, by providing hydrogen-bonding partners, decreased kcat by 10 to 10^4–fold. The same substitutions display very little change in the rate of product H6 exchange, supporting that this hydrophobic pocket affects the substrate-enzyme complex before the transition state. We also provide evidence that hydrophilic residues can insert water molecules into the pocket with detrimental effects to catalysis.

Knowledge management capabilities and organizational performance: an investigation into the effects of knowledge infrastructure and processes on organizational performance

Knowledge is one of the most important assets for surviving in the modern business environment. The effective management of that asset mandates continuous adaptation by organizations, and requires employees to strive to improve the company's work processes. Organizations attempt to coordinate their unique knowledge with traditional means as well as in new and distinct ways, and to transform them into innovative resources better than those of their competitors. As a result, how to manage the knowledge asset has become a critical issue for modern organizations, and knowledge management is considered the most feasible solution. Knowledge management is a multidimensional process that identifies, acquires, develops, distributes, utilizes, and stores knowledge. However, many related studies focus only on fragmented or limited knowledge-management perspectives. In order to make knowledge management more effective, it is important to identify the qualitative and quantitative issues that are the foundation of the challenge of effective knowledge management in organizations. The main purpose of this study was to integrate the fragmented knowledge management perspectives into the holistic framework, which includes knowledge infrastructure capability (technology, structure, and culture) and knowledge process capability (acquisition, conversion, application, and protection), based on Gold's (2001) study. Additionally, because the effect of incentives ̶̶ which is widely acknowledged as a prime motivator in facilitating the knowledge management process ̶̶ was missing in the original framework, this study included the importance of incentives in the knowledge management framework. This study also identified the relationship of organizational performance from the standpoint of the Balanced Scorecard, which includes the customer-related, internal business process, learning & growth, and perceptual financial aspects of organizational performance in the Korean business context. Moreover, this study identified the relationship with the objective financial performance by calculating the Tobin's q ratio. Lastly, this study compared the group differences between larger and smaller organizations, and manufacturing and nonmanufacturing firms in the study of knowledge management. Since this study was conducted in Korea, the original instrument was translated into Korean through the back translation technique. A confirmatory factor analysis (CFA) was used to examine the validity and reliability of the instrument. To identify the relationship between knowledge management capabilities and organizational performance, structural equation modeling (SEM) and multiple regression analysis were conducted. A Student's t test was conducted to examine the mean differences. The results of this study indicated that there is a positive relationship between effective knowledge management and organizational performance. However, no empirical evidence was found to suggest that knowledge management capabilities are linked to the objective financial performance, which remains a topic for future review. Additionally, findings showed that knowledge management is affected by organization's size, but not by type of organization. The results of this study are valuable in establishing a valid and reliable survey instrument, as well as in providing strong evidence that knowledge management capabilities are essential to improving organizational performance currently and making important recommendations for future research.