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PubMed2005

Exosite-driven substrate specificity and function in coagulation.

Macromolecular substrate recognition and serine proteinase specificity lie at the heart of the tightly regulated hemostatic response. Mechanisms established for the less specific serine proteinases of digestion have played a dominant role in guiding investigations of the basis for the narrow specificities exhibited by the coagulation enzymes. These concepts have also dominated the development of specific inhibitors of coagulation for therapeutic purposes. Studies of the enzymology and physical biochemistry of prothrombinase challenge these prevailing ideas by establishing a principal role for exosites within the enzyme in determining substrate recognition and directing the action of the enzyme on its biological substrate. Mechanisms by which narrow protein substrate specificity is achieved by prothrombinase also apply to several other reactions of coagulation. These strategies are increasingly evident in the action of other families of enzymes that act with high specificity on protein substrates. Exosite-driven enzymic function probably represents a widely employed biological strategy for the achievement of high macromolecular substrate specificity.

Animals↗
PubMed1990

Pseudohypophosphatasia: aberrant localization and substrate specificity of alkaline phosphatase in cultured skin fibroblasts.

We explored the biochemical basis for the disorder pseudohypophosphatasia (PsHYPT) in one patient by examining the substrate specificity and localization of alkaline phosphatase (ALP) in cultured dermal fibroblasts. Despite substantial ALP activity, in cell homogenates, toward the artificial substrate 4-methyl-umbelliferyl phosphate (4-MUP), there was a marked deficiency in ALP activity toward the natural substrates pyridoxal 5'-phosphate (PLP) and phosphoethanolamine (PEA), indicating altered substrate specificity. Furthermore, although 4-MUP phosphatase (4-MUP-P'tase) activity was predominantly localized as an ecto-enzyme, the small amount of PLP phosphatase (PLP-P'tase) activity was intracellular. This differential localization was apparent in intact cells, since (1) brief acidification of the medium at 4 degrees C inactivated a majority of the 4-MUP-P'tase activity but only 15% of the PLP-P'tase activity (in contrast to greater than 85% inactivation of both in homogenates), (2) greater than 70% of the 4-MUP-P'tase activity but only 30% of the PLP-P'tase activity was released by phosphatidylinositol-specific phospholipase C (PI-PLC) digestion, and (3) degradation of extracellular PLP was less than 35% of that of disrupted cells. Both 4-MUP- and PLP-P'tase activities were predominantly in a lipid-anchored form that could be converted to a soluble, lipid-free form by PI-PLC digestion. Our findings suggest that the clinical and biochemical presentation of this PSHPT patient results from the production of two aberrant ALP species. One form of ALP has appropriate ectoorientation but is preferentially deficient in activity toward natural substrates; the other ALP species has appropriate substrate specificity but is sequestered from substrates by its intracellular location.

Alkaline Phosphatase↗
PubMed1978

Initiation of human parturition. X. Substrate specificity of phospholipase A2 in human fetal membranes.

The substrate specificity of phospholipase A acitivty of fetal membranes and uterine decidua was investigated with the use of synthetic substrates, and emphasis was on the specificity of fatty acid esters in the sn-2 position of glycerophospholipids. Rat liver mitochondria were also used as an enzyme source for the substrate specificity studies. Phosphatidylethanolamine was found to be hydrolyzed more rapidly than was phosphatidycholine by the phospholipase A activities of human fetal membranes and uterine decidua and of rat liver mitochondria. The phopholipase A2 in fetal membranes preferentially effected the hydrolysis of phosphatidylethanolamines containing specific fatty acids in the sn-2 position in the following order: arachidonic acid greater than oleic acid less than palmitic acid. No remarkable specificity for arachidonyl esters in the sn-2 position of phosphatidylethanolamines was observed for the phospholipase A activities of human uterine decidua or rat liver mitochondria. The results of this study are consistent with the view that human fetal membrane phospholipase A2 that preferentially hydrolyzes the phosphatidylethanolamines that contain arachidonic acid in the sn-2 position is, in part, responsible for the highly selective accumulation of free arachidonic acid in the amniotic fluid of women in labor.

Animals↗
PubMed2003

Improved substrate specificity of water-soluble pyrroloquinoline quinone glucose dehydrogenase by a peptide ligand.

A new approach in altering the substrate specificity of enzyme is proposed using glucose dehydrogenase, with pyrroroquinoine quinone (PQQGDH) as co-factor, as the model. This approach is based on the selection of random peptide phage displayed library. Using an M13 phage-display random peptide library, we have selected peptide ligands. Among the peptide ligands, a 7-mer peptide, composed of Thr-Thr-Ala-Thr-Glu-Tyr-Ser, caused PQQGDH substrate specificity to decrease significantly toward disaccharides, such as maltose and lactose, while a smaller effect was observed toward glucose. Consequently, this peptide narrowed the substrate specificity of PQQGDH, without a significant loss of the enzyme activity.

Amino Acid Sequence↗
PubMed2003

Oligosaccharide library-based assessment of heparan sulfate 6-O-sulfotransferase substrate specificity.

Heparan sulfate mediates numerous complex biological processes. Its action critically depends on the amount and the positions of O-sulfate groups (iduronyl 2-O-sulfates, glucosaminyl 6-O- and 3-O-sulfates) that form binding sites for proteins. The structures and distribution of these protein-binding domains are influenced by the expression and substrate specificity of heparan sulfate biosynthetic enzymes. We describe a general approach to assess substrate specificities of enzymes involved in glycosaminoglycan metabolism, here applied to 6-O-sulfotransferases involved in heparan sulfate biosynthesis. To understand how 2-O-sulfation affects subsequent 6-O-sulfation reactions, the substrate specificity of 6-O-sulfotransferase 3 was probed using substrates from a heparin-based octasaccharide library. Purified 3H-labeled N-sulfated octasaccharides from a library designed to sample 2-O-sulfated motifs were used as sulfate acceptors, 3'-phosphoadenosine 5'-phosphosulfate as sulfate donor, and cell extract from 6-O-sulfotransferase 3-overexpressing 293 cells as enzyme source in the 6-O-sulfotransferase-catalyzed reactions. The first 6-O-sulfate group was preferentially incorporated at the internal glucosamine unit of the octasaccharide substrate. As the reaction proceeded, the octasaccharides acquired three 6-O-sulfate groups. The specificities toward competing octasaccharide substrates, for 6-O-sulfotransferase 2 and 6-O-sulfotransferase 3, were determined using overexpressing 293 cell extracts and purified octasaccharides. Both 6-O-sulfotransferases showed a preference for 2-O-sulfated substrates. The specificity toward substrates with two to three 2-O-sulfate groups was three to five times higher as compared with octasaccharides with no or one 2-O-sulfate group.

Animals↗
PubMed1982

Isoleucyl-tRNA synthetase from Escherichia coli MRE 600. Different pathways of the aminoacylation reaction depending on presence of pyrophosphatase, order of substrate addition in the pyrophosphate exchange, and substrate specificity with regard to ATP analogs.

The substrate specificity of isoleucyl-tRNA synthetase from Escherichia coli MRE 600 with regard to ATP analogs has been compared with the results obtained with isoleucyl-tRNA synthetase from yeast. The enzyme from E. coli is less specific, the two enzymes exhibit different topographies of their active centres. The order of substrate addition to isoleucyl-tRNA synthetase from E. coli MRE 600 has been investigated by bisubstrate kinetics, product inhibition and inhibition by substrate analogs. The inhibition studies were done in the aminoacylation and in the pyrophosphate exchange reaction, the aminoacylation was investigated in the absence and presence of inorganic pyrophosphatase. As found for isoleucyl-tRNA synthetase from yeast, the results of the pyrophosphate exchange studies indicate the possibility of formation of E . Ile-AMP . ATP complexes by random addition of one ATP and one isoleucine molecule, followed by adenylate formation, release of pyrophosphate and subsequent addition of a second molecule of ATP. For the aminoacylation in the absence of pyrophosphatase, a rapid-equilibrium random ter addition of the substrates is found whereas the enzyme from yeast exhibits a steady-state ordered ter-ter mechanism; in the presence of pyrophosphatase the mechanism is bi-uni uni-bi ping-pong similarly as observed for the yeast enzyme. A comparison of inhibition patterns obtained with N(6)-benzyladenosine 5'-triphosphate under different assay conditions (spermine or magnesium ions, addition of pyrophosphatase) indicates that even more than two pathways of the aminoacylation may exist. The catalytic cycles of the two mechanisms derived from the observed orders of substrate addition and product release include the same enzyme substrate complex (E . tRNA . Ile-AMP) for the aminoacyl transfer reaction. The kcat values, however, are considerably different: kcat of the sequential pathway is about 40% lower than kcat of the ping-pong mechanism.

Adenosine Triphosphate↗
PubMed2004

Eukaryotic arylamine N-acetyltransferase. Investigation of substrate specificity by high-throughput screening.

Arylamine N-acetyltransferases (NAT; EC 2.3.1.5) catalyse the transfer of acetyl groups from acetylCoA to xenobiotics, including drugs and carcinogens. The enzyme is found extensively in both eukaryotes and prokaryotes, yet the endogenous roles of NATs are still unclear. In order to study the properties of eukaryotic NATs, high-throughput substrate and inhibitor screens have been developed using pure soluble recombinant Syrian hamster NAT2 (shNAT2) protein. The assay can be used with a wide range of compounds and was used to determine substrate specificity of shNAT2. We describe the expression and characterisation of shNAT2 and also purified recombinant human NAT1 and NAT2, including the use of the assay to explore the substrate specificities of each of the enzymes. Hamster NAT2 has similar substrate specificity to human NAT1, acetylating para-aminobenzoate but not arylhydrazine and hydralazine compounds. The overlapping but distinct substrate-specific activity profiles of human NAT1 and NAT2 were clearly observed from the screen. Naturally occurring compounds were tested as substrates or inhibitors of shNAT2 and succinylCoA was found to be a potent inhibitor of shNAT2.

Animals↗
PubMed2001

Modeling, mutagenesis, and structural studies on the fully conserved phosphate-binding loop (loop 8) of triosephosphate isomerase: toward a new substrate specificity.

Loop 8 (residues 232-242) in triosephosphate isomerase (TIM) is a highly conserved loop that forms a tight binding pocket for the phosphate moiety of the substrate. Its sequence includes the fully conserved, solvent-exposed Leu238. The tight phosphate-binding pocket explains the high substrate specificity of TIM being limited to the in vivo substrates dihydroxyacetone-phosphate and D-glyceraldehyde-3-phosphate. Here we use the monomeric variant of trypanosomal TIM for exploring the structural consequences of shortening this loop. The mutagenesis, guided by extensive modeling calculations and followed up by crystallographic characterization, is aimed at widening the phosphate-binding pocket and, consequently, changing the substrate specificity. Two new variants were characterized. The crystal structures of these variants indicate that in monomeric forms of TIM, the Leu238 side-chain is nicely buried in a hydrophobic cluster. Monomeric forms of wild-type dimeric TIM are known to exist transiently as folding intermediates; our structural analysis suggests that in this monomeric form, Leu238 of loop 8 also adopts this completely buried conformation, which explains its full conservation across the evolution. The much wider phosphate-binding pocket of the new variant allows for the development of a new TIM variant with a different substrate specificity.

Amino Acid Sequence↗
PubMed2004

Assessment of arginine 97 and lysine 72 as determinants of substrate specificity in cytochrome P450 2C9 (CYP2C9).

CYP2C9 is distinguished by a preference for substrates bearing a negative charge at physiological pH. Previous studies have suggested that CYP2C9 residues R97 and K72 may play roles in determining preference for anionic substrates by interaction at the active site or in the access channel. The aim of the present study was to assess the role of these two residues in determining substrate selectivity. R97 and K72 were substituted with negative, uncharged polar and hydrophobic residues using a degenerate polymerase chain reaction-directed strategy. Wild-type and mutant enzymes were expressed in bicistronic format with human cytochrome P450 reductase in Escherichia coli. Mutation of R97 led to a loss of holoenzyme expression for R97A, R97V, R97L, R97T, and R97E mutants. Low levels of hemoprotein were detected for R97Q, R97K, R97I, and R97P mutants. Significant apoenzyme was observed, suggesting that heme insertion or protein stability was compromised in R97 mutants. These observations are consistent with a structural role for R97 in addition to any role in substrate binding. By contrast, all K72 mutants examined (K72E, K72Q, K72V, and K72L) could be expressed as hemoprotein at levels comparable to wild-type. Type I binding spectra were obtained with wild-type and K72 mutants using diclofenac and ibuprofen. Mutation of K72 had little or no effect on the interaction with these substrates, arguing against a critical role in determining substrate specificity. Thus, neither residue appears to play a role in determining substrate specificity, but a structural role for R97 can be proposed consistent with recently published crystallographic data for CYP2C9 and CYP2C5.

Animals↗
PubMed1991

Multiple determinants for the high substrate specificity of an angiotensin II-forming chymase from the human heart.

Human heart chymase, a chymotrypsin-like serine proteinase that hydrolyzes the Phe8-His9 bond in angiotensin I (Ang I) to yield the octapeptide hormone angiotensin II (Ang II) and His-Leu, is the most specific, efficient Ang II-forming enzyme described. Other mammalian chymases display a much broader substrate specificity. To better define its substrate specificity, we have mapped the extended substrate-binding site of human heart chymase using Ang I analogs. The enzyme has a preference for aromatic amino acids phenylalanine, tyrosine, and tryptophan at the P1 site. At the S2 subsite there is a significant preference for proline over hydrophobic or hydrophilic amino acids. There is no clear preference for hydrophobic or hydrophilic amino acids at the S'1 and S'2 subsites, but an Ang I analog containing a P'1 proline is not hydrolyzed and one with a P'2 proline is hydrolyzed poorly. An increasing reduction in reactivity occurs when the P position amino acids in Ang I are deleted sequentially from the N terminus. An increase or decrease in the length of the His-Leu leaving group also produces a marked decrease in reactivity. No single determinant in Ang I is preeminently required for efficient catalysis, but several factors acting synergistically appear to be important. Thus, we propose that ideal substrates for human heart chymase should contain the structure nXaa-Pro-[Phe, Tyr, or Trp]-Yaa-Yaa, where n greater than or equal to 6; Xaa = any amino acid; Yaa = any amino acid except proline. This structure exists in Ang I and neurotensin, both of which are good substrates for human heart chymase. These findings indicate that the selection of the scissile bond by the extended substrate-binding site of human heart chymase is more restricted than that in other chymases.

Amino Acid Sequence↗
PubMed1995

Human hepatic and lipoprotein lipase: the loop covering the catalytic site mediates lipase substrate specificity.

Hepatic lipase (HL) and lipoprotein lipase (LPL) are key enzymes that mediate the hydrolysis of triglycerides (TG) and phospholipids (PL) present in circulating plasma lipoproteins. Relative to triacylglycerol hydrolysis, HL displays higher phospholipase activity than LPL. The structural basis for this difference in substrate specificity has not been definitively established. We recently demonstrated that the 22-amino acid loops ("lids") covering the catalytic sites of LPL and HL are critical for the interaction with lipid substrate (Dugi, K.A., Dichek, H.L., Talley, G.D., Brewer, H.B., Jr., and Santamarina-Fojo, S. (1992) J. Biol. Chem. 267, 25086-25091). To determine whether the lipase lid plays a role in conferring the different substrate specificities of HL and LPL, we have generated four chimeric lipases. Characterization of these chimeric enzymes using TG (triolein and tributyrin) or PL (dioleoylphosphatidylcholine (DOPC) vesicles, DOPC proteoliposomes, and DOPC-mixed liposomes) substrates demonstrated marked differences between their relative PL/TG hydrolyzing activities. Chimeric LPL containing the lid of HL had reduced triolein hydrolyzing activity (49% of the wild type), but increased phospholipase activity in DOPC vesicle, DOPC proteoliposome, and DOPC-mixed liposome assay systems (443, 628, and 327% of wild-type LPL, respectively). In contrast, chimeric HL containing the LPL lid was more active against triolein (123% of the wild type) and less active against DOPC (23, 0, and 30%, respectively) than normal HL. Similar results were obtained when the lipase lids were exchanged in chimeric enzymes containing the NH2-terminal end of LPL and the COOH-terminal domain of HL. Exchange of the LPL and HL lids resulted in a reversal of the phospholipase/neutral lipase ratio, establishing the important role of this region in mediating substrate specificity. In summary, the lid covering the catalytic domains in LPL and HL plays a crucial role in determining lipase substrate specificity. The lid of LPL confers preferential triglyceride hydrolysis, whereas the lid of HL augments phospholipase activity. This study provides new insight into the structural basis for the observed in vivo differences in LPL and HL function.

Amino Acid Sequence↗
PubMed2003

Mutual conversion of substrate specificities of Thermoactinomyces vulgaris R-47 alpha-amylases TVAI and TVAII by site-directed mutagenesis.

Thermoactinomyces vulgaris R-47 produces two alpha-amylases, TVAI and TVAII, differing in substrate specificity from each other. TVAI favors high-molecular-weight substrates like starch, and scarcely hydrolyzes cyclomaltooligosaccharides (cyclodextrins) with a small cavity. TVAII favors low-molecular-weight substrates like oligosaccharides, and can efficiently hydrolyze cyclodextrins with various sized cavities. To understand the relationship between the structure and substrate specificity of these enzymes, we precisely examined the roles of key residues for substrate recognition by X-ray structural and kinetic parameter analyses of mutant enzymes and successfully obtained mutants in which the substrate specificity of each enzyme is partially converted into that of another.

Binding Sites↗
PubMed2001

Probing molecular function of trypanosomal sialidases: single point mutations can change substrate specificity and increase hydrolytic activity.

Sialidases are present on the surface of several trypanosomatid protozoan parasites. They are highly specific for sialic acid linked in alpha-(2,3) to a terminal beta-galactose and include the strictly hydrolytic enzymes and trans-sialidases (sialyl-transferases). Based on the structural comparison of the sialidase from Trypanosoma rangeli and the trans-sialidase from T. cruzi (the agent of Chagas' disease in humans), we have explored the role of specific amino acid residues sought to be important for substrate specificity. The substitution of a conserved tryptophanyl residue in the two enzymes, Trp312/313-Ala, changed substrate specificity, rendering the point mutants capable to hydrolyze both alpha-(2,3)- and alpha-(2,6)-linked sialoconjugates. The same mutation abolished sialyl-transferase activity, indicating that transfer (but not hydrolysis) requires a precise orientation of the bound substrate. The exchange substitution of another residue that modulates oligosaccharide binding, Gln284-Pro, was found to significantly increase the hydrolytic activity of sialidase, and residue Tyr119 was confirmed to be part of a second binding site for the acceptor substrate in trans-sialidase. Together with the structural information, these results provide a consistent framework to account for the unique enzymatic properties of trypanosome trans-sialidases.

Amino Acid Substitution↗
PubMed1987

The influence of basic residues on the substrate specificity of protein kinase C.

The substrate specificity of protein kinase C has been examined using a series of synthetic peptide analogs of glycogen synthase, ribosomal protein S6, and the epidermal growth factor receptor. The glycogen synthase analog peptide Pro1-Leu-Ser-Arg-Thr-Leu-Ser-Val-Ala-Ala10 was phosphorylated at Ser7 with a Km of 40.3 microM. Peptide phosphorylation was strongly dependent on Arg4. When lysine was substituted for Arg4 the Km was increased approximately 20-fold. Addition of basic residues on either the NH2-terminal or COOH-terminal side of the phosphorylation site of the glycogen synthase peptide improved the kinetics of peptide phosphorylation. The analog Pro-Leu-Ser-Arg-Thr-Leu-Ser-Val-Ala-Ala-Lys-Lys was phosphorylated with a Km of 4.1 microM. Substitution of Ser7 with threonine increased the apparent Km to 151 microM. The truncated peptide Pro1-Leu-Ser-Arg-Thr-Leu-Ser-Val8 was phosphorylated with similar kinetic constants to the parent peptide, however, deletion of Val8 increased the apparent Km to 761 microM. The ribosomal peptide S6-(229-239) was phosphorylated with a Km of approximately 0.5 microM predominantly on Ser236 and is one of the most potent synthetic peptide substrates reported for a protein kinase. The apparent Km for S6 peptide phosphorylation was increased by either deletion of the NH2-terminal 3 residues Ala229-Arg-231 or by substitution of Arg238 on the COOH-terminal side of the phosphorylation site with alanine. This analog peptide, [Ala238]S6-(229-239) was phosphorylated with an approximate 6-fold reduction in Vmax and a switch in the preferred site of phosphorylation from Ser236 to Ser235. These results support the concept that basic residues on both sides of the phosphorylation site can have an important influence on the kinetics of phosphorylation and site specificity of protein kinase C.

Animals↗
PubMed1991

Substrate specificity and pH dependence of homogeneous wheat germ acid phosphatase.

The broad substrate specificity of a homogeneous isoenzyme of wheat germ acid phosphatase (WGAP) was extensively investigated by chromatographic, electrophoretic, NMR, and kinetic procedures. WGAP exhibited no divalent metal ion requirement and was unaffected upon incubation with EDTA or o-phenanthroline. A comparison of two catalytically homogeneous isoenzymes revealed little difference in substrate specificity. The specificity of WGAP was established by determining the Michaelis constants for a wide variety of substrates. p-Nitrophenyl phosphate, pyrophosphate, tripolyphosphate, and ATP were preferred substrates while lesser activities were seen toward sugar phosphates, trimetaphosphate, phosphoproteins, and (much less) phosphodiesters. An extensive table of Km and Vmax values is given. The pathway for the hydrolysis of trimetaphosphate was examined by colorimetric and 31P NMR methods and it was found that linear tripolyphosphate is not a free intermediate in the enzymatic reaction. In contrast to literature reports, homogeneous wheat germ acid phosphatase exhibits no measurable carboxylesterase activity, nor does it hydrolyze phenyl phosphonothioate esters or phytic acid at significant rates.

6-Phytase↗
PubMed2001

Novel substrate specificity of designer 3-isopropylmalate dehydrogenase derived from Thermus thermophilus HB8.

Redesigning of an enzyme for a new catalytic reaction and modified substrate specificity was exploited with 3-isopropylmalate dehydrogenase (IPMDH). Point-mutation on Gly-89, which is not in the catalytic site but near it, was done by changing it to Ala, Ser, Val, and Pro, and all the mutations changed the substrate specificity. The mutant enzymes showed higher catalytic efficiency (kcat/Km) than the native IPMDH when malate was used as a substrate instead of 3-isopropylmalate. More interestingly, an additional insertion of Gly between Gly-89 and Leu-90 significantly altered the substrate-specificity, although the overall catalytic activity was decreased. Particularly, this mutant turned out to efficiently accept D-lactic acid, which was not accepted as a substrate by wild-type IPMDH at all. These results demonstrate the opportunity for creating nove,enzymes by modification of amino acid residues that do not directly participate in catalysis, or by insertion of additional residues.

3-Isopropylmalate Dehydrogenase↗
PubMed2003

Substrate specificities and excision kinetics of DNA glycosylases involved in base-excision repair of oxidative DNA damage.

Reactive oxygen-derived species such as free radicals are formed in living cells by normal metabolism and exogenous sources, and cause a variety of types of DNA damage such as base and sugar damage, strand breaks and DNA-protein cross-links. Living organisms possess repair systems that repair DNA damage. Oxidative DNA damage caused by free radicals and other oxidizing agents is mainly repaired by base-excision repair (BER), which involves DNA glycosylases in the first step of the repair process. These enzymes remove modified bases from DNA by hydrolyzing the glycosidic bond between the modified base and the sugar moiety, generating an apurinic/apyrimidinic (AP) site. Some also possess AP lyase activity that subsequently cleaves DNA at AP sites. Many DNA glycosylases have been discovered and isolated, and their reaction mechanisms and substrate specificities have been elucidated. Most of the known products of oxidative damage to DNA are substrates of DNA glycosylases with broad or narrow substrate specificities. Some possess cross-activity and remove both pyrimidine- and purine-derived lesions. Overlapping activities between enzymes also exist. Studies of substrate specificities have been performed using either oligodeoxynucleotides with a single modified base embedded at a specific position or damaged DNA substrates containing a multiplicity of pyrimidine- and purine-derived lesions. This paper reviews the substrate specificities and excision kinetics of DNA glycosylases that have been investigated with the use of gas chromatography/mass spectrometry and DNA substrates with multiple lesions.

Animals↗
PubMed2002

Analyses of substrate specificity of the desulfurizing bacterium Mycobacterium sp. G3.

The substrate specificity of Mycobacterium sp. G3 with desulfurization activity against dibenzothiophene (DBT) was investigated. Desulfurization reactions were carried out using a concentrated cell suspension of G3. The conversion from 4,6-dipropyl DBT, one of the sulfur-containing compounds that is difficult to desulfurize in diesel oil, to 2-hydroxy-3,3'-dipropylbiphenyl as an end -product of the desulfurization reaction was found in the water reaction system and in the oil/water two-phase reaction system. 4,6-Dibutyl DBT and 4,6-dipentyl DBT were metabolized to the hydroxybiphenyl form via the sulfone form in the water reaction system. These results indicate that G3 has high membrane permeability and superior substrate specificity for high molecular weight alkyl DBTs, which are represented by 4,6-dipentyl DBT as C10-DBT. Furthermore, G3 could desulfurize diesel oil, and the sulfur concentration was decreased from 116 mg l(-1) to 48 mg l(-1) within 24 h.

Journal Article↗