21 research outputs found
Prostaglandin Synthesis in the Coral Plexaura homomalla : Control of Prostaglandin Stereochemistry at Carbon 15 by Cyclooxygenases. Prostaglandiinide s\ufcntees korallis Plexaura homomalla : ts\ufcklooks\ufcgenaasi stereospetsiifilisuse struktuurilised determinandid
Prostaglandiinide s\ufcntees korallis Plexaura homomalla : ts\ufcklooks\ufcgenaasi stereospetsiifilisuse struktuurilised determinandid. Prostaglandin Synthesis in the Coral Plexaura homomalla : Control of Prostaglandin Stereochemistry at Carbon 15 by Cyclooxygenases
Substrate Specifity Of Porcine Pancreatic Lipase Studied In Terms Of The Steady-State Kinetics Binding And Rate Constants
The steady-state kinetics binding constants have been rarely determined for emulsified lipase
substrates since the apparent Michaelis constant has the dimension of the emulsion surface area in
this case [1,2] which typically could not be determined precisely. On the other hand, only a
combination of binding and rate parameters could be determined in experiments with substrate
monolayers [3,4], and the range of suitable substratesis strictly limited in these experiments due to
requirements on the stability of monolayers, productsolubility, etc. [4].
In this paper we review data on the substrate specificity of porcine pancreatic lipase on emulsified
triacylglycerolsubstrates studied in terms of the steady-state binding and rate constants in the assay
system lipase/colipase/micellar NaTDC'/-triacylglycerol emulsion’
Evaluation of Zn2+- and Cu2+-Binding Affinities of Native Cu,Zn-SOD1 and Its G93A Mutant by LC-ICP MS
The tight binding of Cu and Zn ions to superoxide dismutase 1 (SOD1) maintains the protein stability, associated with amyotrophic lateral sclerosis (ALS). Yet, the quantitative studies remain to be explored for the metal-binding affinity of wild-type SOD1 and its mutants. We have investigated the demetallation of Cu,Zn-SOD1 and its ALS-related G93A mutant in the presence of different standard metal ion chelators at varying temperatures by using an LC-ICP MS-based approach and fast size-exclusion chromatography. Our results showed that from the slow first-order kinetics both metal ions Zn2+ and Cu2+ were released simultaneously from the protein at elevated temperatures. The rate of the release depends on the concentration of chelating ligands but is almost independent of their metal-binding affinities. Similar studies with the G93A mutant of Cu,Zn-SOD1 revealed slightly faster metal-release. The demetallation of Cu,Zn-SOD1 comes always to completion, which hindered the calculation of the KD values. From the Arrhenius plots of the demetallation in the absence of chelators ΔH‡ = 173 kJ/mol for wt and 191 kJ/mol for G93A mutant Cu,Zn-SOD1 was estimated. Obtained high ΔH values are indicative of the occurrence of protein conformational changes before demetallation and we concluded that Cu,Zn-SOD1 complex is in native conditions kinetically inert. The fibrillization of both forms of SOD1 was similar
The structure of coral allene oxide synthase reveals a catalase adapted for metabolism of a fatty acid hydroperoxide
8R-Lipoxygenase and allene oxide synthase (AOS) are parts of a naturally occurring fusion protein from the coral Plexaura homomalla. AOS catalyses the production of an unstable epoxide (an allene oxide) from the fatty acid hydroperoxide generated by the lipoxygenase activity. Here, we report the structure of the AOS domain and its striking structural homology to catalase. Whereas nominal sequence identity between the enzymes had been previously described, the extent of structural homology observed was not anticipated, given that this enzyme activity had been exclusively associated with the P450 superfamily, and conservation of a catalase fold without catalase activity is unprecedented. Whereas the heme environment is largely conserved, the AOS heme is planar and the distal histidine is flanked by two hydrogen-bonding residues. These critical differences likely facilitate the switch from a catalatic activity to that of a fatty acid hydroperoxidase