Esterification of chitosan with adipic acid catalyzed by immobilized Candida antarctica lipase B was carried out in this study. Response surface methodology (RSM) based on a four-factor- five-level small central composite design (SCCD) was employed to model and analyze the reaction. A total of 21 experiments representing different combinations of the four reaction parameters including ch...

within the past few years, neat scheme has been overturned by the discovery that rna can act as an enzyme. what does the starting finding of rna enzymes imply? thre first implication is that one can no longer assume a protein lies behind every catalytic activity of the cell. it now appears that several of the operations that tailor an ran molecule into its final form are at least in part cataly...

An enzyme activity responsible for the formation of 5’phosphoribosylamine from ribose 5-phosphate and a nitrogen donor was prepared from livers of ducks, chickens, and pigeons. This enzyme activity is distinct from ribosylpryophosphate 5-phosphate amidotransferase (EC 2.4.2.14), which catalyzes the formation of 5’-phosphoribosylamine from ribosylpyrophosphate 5-phosphate and glutamine. The enzy...

The clinical effectiveness of tissue conditioners is influenced by their gelation characteristics and viscoelastic properties after gelation. The purpose of this study was to evaluate the effect of addition of ethyl alcohol (EtOH) on these properties, and to compare the effect of EtOH with that of the powder/liquid (P/L) ratio. Three tissue conditioners were used in this study. The gelation tim...

This enzyme is provisionally referred to as “malic” enzyme. The present paper deals with further observations on the kinetics and other properties of the purified enzyme.’ The enzyme is totally inactive in the absence of Mn++. Mg++ can replace Mn++ but is less effective. Further evidence has been obtained indicating that free oxalacetate is not an intermediate in Reaction 1 and that both Reacti...

The Old Yellow Enzyme has been shown to catalyze efficiently the NADPH-linked reduction of nitro-olefins. The reduction of the nitro-olefin proceeds in a stepwise fashion, with formation of a nitronate intermediate that is freely dissociable from the enzyme. The first step involves hydride transfer from the enzyme-reduced flavin to carbon 2 of the nitro-olefin. The protonation of the nitronate ...

Both the adenylylated and unadenylylated forms of Escherichia coli glutamine synthetase catalyze the formation of pyrrolidone carboxylate from glutamate in the presence of ATP and divalent metal ions (Mg++ or Mn++) and in the absence of ammonia. The unadenylylated enzyme catalyzes this reaction more rapidly with Mg++ than with Mn++, while the adenylylated enzyme catalyzes it more rapidly with M...

Both the adenylylated and unadenylylated forms of Escherichia coli glutamine synthetase catalyze the formation of pyrrolidone carboxylate from glutamate in the presence of ATP and divalent metal ions (Mg++ or Mn++) and in the absence of ammonia. The unadenylylated enzyme catalyzes this reaction more rapidly with Mg++ than with Mn++, while the adenylylated enzyme catalyzes it more rapidly with M...

Peptides made of D-amino acids, as the enantiomer of corresponding L-peptides, are able to resist proteolysis. It is, however, unclear or much less explored whether or how D-amino acids affect the cellular response of supramolecular nanofibers formed by enzyme-triggered self-assembly of D-peptides. In this work, we choose a cell compatible molecule, Nap-L-Phe-L-Phe-L-(p)Tyr (LLL-1P), and system...