The purpose of this study is to summarize the current knowledge of the enzymes which are involved in the hydrolysis of cyanide, i.e., cyanide hydratases (CHTs; EC 4.2.1.66) and cyanide dihydratases (CynD; EC 3.5.5.1). CHTs are probably exclusively produced by filamentous fungi and widely occur in these organisms; in contrast, CynDs were only found in a few bacterial genera. CHTs differ from CynDs in their reaction products (formamide vs. formic acid and ammonia, respectively). Several CHTs were also found to transform nitriles but with lower relative activities compared to HCN. Mutants of CynDs and CHTs were constructed to study the structure-activity relationships in these enzymes or to improve their catalytic properties. The effect of the C-terminal part of the protein on the enzyme activity was determined by constructing the corresponding deletion mutants. CynDs are less active at alkaline pH than CHTs. To improve its bioremediation potential, CynD from Bacillus pumilus was engineered by directed evolution combined with site-directed mutagenesis, and its operation at pH 10 was thus enabled. Some of the enzymes have been tested for their potential to eliminate cyanide from cyanide-containing wastewaters. CynDs were also used to construct cyanide biosensors.

• MeSH
• Bacteria enzymologie   MeSH
• biosenzitivní techniky * MeSH
• biotransformace MeSH
• dehydratasy chemie   genetika   metabolismus   MeSH
• houby enzymologie   MeSH
• hydrolasy chemie   genetika   metabolismus   MeSH
• hydrolýza MeSH
• koncentrace vodíkových iontů MeSH
• kyanidy analýza   metabolismus   MeSH
• látky znečišťující životní prostředí analýza   metabolismus   MeSH
• mutační analýza DNA MeSH
• mutantní proteiny genetika   metabolismus   MeSH
• proteinové inženýrství MeSH
• stabilita enzymů MeSH
• vztahy mezi strukturou a aktivitou MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• přehledy MeSH

A panel of lipases was screened for the selective acetylation and alcoholysis of silychristin and silychristin peracetate, respectively. Acetylation at primary alcoholic group (C-22) of silychristin was accomplished by lipase PS (Pseudomonas cepacia) immobilized on diatomite using vinyl acetate as an acetyl donor, whereas selective deacetylation of 22-O-acetyl silychristin was accomplished by Novozym 435 in methyl tert-butyl ether/ n-butanol. Both of these reactions occurred without diastereomeric discrimination of silychristin A and B. Both of these enzymes were found to be capable to regioselective deacetylation of hexaacetyl silychristin to afford penta-, tetra- and tri-acetyl derivatives, which could be obtained as pure synthons for further selective modifications of the parent molecule.

• MeSH
• acetáty chemická syntéza   MeSH
• acetylace MeSH
• bakteriální proteiny metabolismus   MeSH
• biokatalýza MeSH
• Burkholderia cepacia enzymologie   MeSH
• enzymy imobilizované metabolismus   MeSH
• lipasa metabolismus   MeSH
• molekulární struktura MeSH
• registrace MeSH
• silymarin chemie   MeSH
• stereoizomerie MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH