Operational Stability of Enzymes.

Abstract

The method of measuring enzyme deactivation by monitoring necessary addition of fresh enzyme to keep a constant degree of conversion in a CSTR at constant [E] x tau, the product of concentration of active enzyme [E] and residence time tau, was successfully applied to acylase I from porcine kidney and Aspergillus oryzae fungus. Fungal enzyme was found to be more stable than kidney enzyme. Activation by both Co2+ and Zn2+ ions also yielded increased operational enzyme stability: Co2+ and Zn2+ are better stabilizers than activators. Mg2+ and Ca2+ are found to be neither activators nor stabilizers. Fungal acylase partially deactivated by exposition to a metal-free medium in the CSTR was reactivated by addition of Zn2+, demonstrating that loss of Zn2+ from the enzyme molecule is mainly responsible for deactivation in a continuous reactor.

Enzymatic Racemisation and its Application to Synthetic Biotransformations

“…[92] Currently, several hundred tons of l-methionine are produced annually by kinetic resolution in an enzyme membrane reactor. [93] Previously, kinetic resolution of N-acetyl-dl-amino acids was achieved by using an enantiospecific l-amino acylase from Aspergillus oryzae which hydrolyses only the lenantiomer to produce a mixture of the corresponding l-amino acid and unreacted N-acetyl-d-amino acid. After separation of the formed l-amino acid by crystallisation, the remaining N-acetyl-d-amino acid was recycled by thermal racemisation under drastic conditions according to a classic protocol.…”

Discovery of 7-[18F]Fluorotryptophan as a Novel Positron Emission Tomography (PET) Probe for the Visualization of Tryptophan Metabolism in Vivo

“…5-BrTrp ( 24 ) was prepared from racemic Ac-5-BrTrp-OH [( RS )- 25 ] via enzymatic deacetylation using acylase I from porcine liver in 20% yield (Figure ). Subsequent N -Boc and O - t Bu protection steps followed by Miyaura borylation furnished the respective pinacol boronate (Bpin) ester 26 in 47% yield over three steps. Alternatively, 24 was treated with AcO t Bu in the presence of HClO 4 affording N in - t Bu substituted amino ester 27 .…”

NAD(H)‐PEG Swing Arms Improve Both the Activities and Stabilities of Modularly‐Assembled Transhydrogenases Designed with Predictable Selectivities

“…The thermodynamic and kinetic stability measurements are not necessarily predictive of the operational stability, as they do not capture enzyme stability under the relevant operating conditions of the reaction. [27] The effects of the additional swing arms on the thermal stabilities of the PEGylated FDH-SpyCatcher mutants were investigated (Figure 2c). The residual FDH activity of each enzyme was measured after 30 minutes of heating at either 45 °C or 55 °C, and compared to that of the same species before heating.…”