Characterization of an α-amino-ɛ-caprolactam racemase with broad substrate specificity from Citreicella sp. SE45.

α-Amino-ε-caprolactam (ACL) racemizing activity was detected in a putative dialkylglycine decarboxylase (EC 4.1.1.64) from Citreicella sp. SE45. The encoding gene of the enzyme was cloned and transformed in Escherichia coli BL21 (DE3). The molecular mass of the enzyme was shown to be 47.4 kDa on SDS-polyacrylamide gel electrophoresis. The enzymatic properties including pH and thermal optimum and stabilities were determined. This enzyme acted on a broad range of amino acid amides, particularly unbranched amino acid amides including L-alanine amide and L-serine amide with a specific activity of 17.5 and 21.6 U/mg, respectively. The K m and V max values for D- and L-ACL were 5.3 and 2.17 mM, and 769 and 558 µmol/min.mg protein, respectively. Moreover, the turn over number (K cat) and catalytic efficiency (K cat/K m ) of purified ACL racemase from Citreicella sp. SE45 using L-ACL as a substrate were 465 S-1 and 214 S-1mM-1, respectively. The new ACL racemase from Citreicella sp. SE45 has a potential to be used as the biocatalytic application.

Hydroxynitrile lyases from cyanogenic millipedes: molecular cloning, heterologous expression, and whole-cell biocatalysis for the production of (R)-mandelonitrile.

Hydroxynitrile lyases (HNLs), which are key enzymes in cyanogenesis, catalyze the cleavage of cyanohydrins into carbonyl compounds and hydrogen cyanide. Since HNLs also catalyze the reverse reaction, they are used industrially for the asymmetric synthesis of cyanohydrins, which are valuable building blocks of pharmaceuticals and fine chemicals. HNLs have been isolated from cyanogenic plants and bacteria. Recently, an HNL from the cyanogenic millipede Chamberlinius hualienensis was shown to have the highest specific activity for (R)-mandelonitrile synthesis, along with high stability and enantioselectivity. However, no HNLs have been isolated from other cyanogenic millipedes. We identified and characterized HNLs from 10 cyanogenic millipedes in the Paradoxosomatidae and Xystodesmidae. Sequence analyses showed that HNLs are conserved among cyanogenic millipedes and likely evolved from one ancestral gene. The HNL from Parafontaria tonominea was expressed in Escherichia coli SHuffle T7 and showed high specific activity for (R)-mandelonitrile synthesis and stability at a range of pHs and temperatures. The stability of millipede HNLs is likely due to disulfide bond(s). The E. coli cells expressing HNL produced (R)-mandelonitrile with 97.6% enantiomeric excess without organic solvents. These results demonstrate that cyanogenic millipedes are a valuable source of HNLs with high specific activity and stability.

Pheophytin a, a low molecular weight compound found in the marine brown alga Sargassum fulvellum, promotes the differentiation of PC12 cells.

We identified and characterized a neurodifferentiation compound from the marine brown alga Sargassum fulvellum collected from the Japanese coastline. Several instrumental analyses revealed the compound to be pheophytin a. Pheophytin a did not itself promote neurite outgrowth of PC12 cells. However, when PC12 cells were treated with a low concentration of pheophytin a (3.9 microg/ml) in the presence of a low level of nerve growth factor (10 ng/ml), the compound produced neurite outgrowth similar to that produced by a high level of nerve growth factor (50 ng/ml). Pheophytin a also enhanced signal transduction in the mitogen-activated protein kinase signaling pathway, which is also induced by nerve growth factor. The effect of pheophytin a on neurite outgrowth of PC12 cells was completely blocked by U0126, a representative mitogen-activated protein kinase kinase inhibitor. These results suggest that pheophytin a enhances the neurodifferentiation of PC12 cells in the presence of a low level of nerve growth factor and that this effect is mediated by activation of a mitogen-activated protein kinase signaling pathway.

A sacrificial millipede altruistically protects its swarm using a drone blood enzyme, mandelonitrile oxidase.

Soldiers of some eusocial insects exhibit an altruistic self-destructive defense behavior in emergency situations when attacked by large enemies. The swarm-forming invasive millipede, Chamberlinius hualienensis, which is not classified as eusocial animal, exudes irritant chemicals such as benzoyl cyanide as a defensive secretion. Although it has been thought that this defensive chemical was converted from mandelonitrile, identification of the biocatalyst has remained unidentified for 40 years. Here, we identify the novel blood enzyme, mandelonitrile oxidase (ChuaMOX), which stoichiometrically catalyzes oxygen consumption and synthesis of benzoyl cyanide and hydrogen peroxide from mandelonitrile. Interestingly the enzymatic activity is suppressed at a blood pH of 7, and the enzyme is segregated by membranes of defensive sacs from mandelonitrile which has a pH of 4.6, the optimum pH for ChuaMOX activity. In addition, strong body muscle contractions are necessary for de novo synthesis of benzoyl cyanide. We propose that, to protect its swarm, the sacrificial millipede also applies a self-destructive defense strategy-the endogenous rupturing of the defensive sacs to mix ChuaMOX and mandelonitrile at an optimum pH. Further study of defensive systems in primitive arthropods will pave the way to elucidate the evolution of altruistic defenses in the animal kingdom.

In Silico Identification for α-Amino-ε-Caprolactam Racemases by Using Information on the Structure and Function Relationship.

In silico identification for enzymes having desired functions is attractive because there is a possibility that numerous desirable enzymes have been deposited in databases. In this study, α-amino-ε-caprolactam (ACL) racemases were searched from the NCBI protein database. Four hundred thirteen fold-type I pyridoxal 5'-phosphate-dependent enzymes which are considered to contain sequences of ACL racemase were firstly obtained by submitting the sequence of ACL racemase from Achromobacter obae to the database. By identifying Lys241 as a key amino acid residue, 13 candidates for ACL racemase were selected. Then, putative ACL racemase genes were synthesized as codon-optimized sequences for expression in Escherichia coli. They were subcloned and expressed in E. coli BL21 and underwent His-tag purification. ACL and amino acid amide racemizing activities were detected among ten of the candidates. The locus tags Oant_4493, Smed_5339, and CSE45_2055 derived from Ochrobactrum anthropi ATCC49188, Sinorhizobium medicae WSM 419, and Citreicella sp. SE45, respectively, showed higher racemization activity against D- and L-ACLs rather than that of ACL racemase from A. obae. Our results demonstrate that the newly discovered ACL racemases were unique from ACL racemase from A. obae and might be useful for applications in dynamic kinetic resolution for D- or L-amino acid production.

Structure elucidation of acylsucrose derivatives from Atractylodes lanceae rhizome and Atractylodes rhizome.

The mass chromatographic fingerprints of the water extracts of Atractylodes rhizome and Atractylodes lancea rhizome were analyzed by LC-MS. Three new acylsucrose derivatives [2,6,3',6'-tetra(3-methylbutanoyl)sucrose (1), 2,4,3',6'-tetra(3-methylbutanoyl)sucrose (2), and a mixture of 3',4',6'-tris(3-methylbutanoyl)-1'-(2-methylbutanoyl)sucrose and 1',3',4',6'-tetra(3-methylbutanoyl)sucrose (6)), along with three known acylsucroses (2,6,3',4'-tetra(3-methylbutanoyl)sucrose (3), 2,4,3',4'-tetra(3-methylbutanoyl)sucrose (4) and a mixture of 2,3',6'-tris(3-methylbutanoyl)-1'-(2-methylbutanoyl)sucrose and 2,1',3',6'-tetra(3-methylbutanoyl)sucrose (5)] were isolated as the marker compounds of Atractylodes rhizome and Atractylodes lancea rhizome. The structures of the compounds were elucidated by MS/MS analyses and NMR experiments.

Prediction of cyclooxygenase inhibitory activity of curcuma rhizome from chromatograms by multivariate analysis.

The potential use of partial least square regression (PLS-R) models for the prediction of biological activities of a herbal drug based on its liquid chromatography (LC) profile was verified using various extracts of Curcuma phaeocaulis and their cyclooxygenase-2 (COX-2) inhibitory activities as the model experiment. The correlation of practically measured inhibitory activities and predicted values by PLS-R analysis was quite good (correlation coefficient=0.9935) and the possibility of transforming chromatographic information into a measure of biological activity was confirmed. In addition, furanodienone and curcumenol were identified as the major active anti-inflammatory constituents of C. phaeocaulis, through detailed analysis of the regression vector, followed by isolation of these compounds and their COX-2 inhibitory assays. The selectivity indices (SI), IC(50) of COX-1/IC(50) of COX-2, of both compounds were higher than that of indomethacin and it is considered that furanodienone and curcumenol are the most promising compounds as lead anti-inflammatory agents.

Vitamin B(12), a chlorophyll-related analog to pheophytin a from marine brown algae, promotes neurite outgrowth and stimulates differentiation in PC12 cells.

We previously isolated an analog to chlorophyll-related compounds, pheophytin a, from the marine brown alga Sargassum fulvellum and demonstrated that it is a neurodifferentiation compound. In the current study, we investigated the effects of the pheophytin a analog vitamin B(12) on PC12 cell differentiation. In the presence of a low level of nerve growth factor (10 ng ml(-1)), vitamin B(12 )demonstrated neurite outgrowth-promoting activity in PC12 cells. The effect was dose-dependent in the range of 6-100 muM. In the absence of nerve growth factor, vitamin B(12) did not promote differentiation. To investigate the mechanism for this effect, we conducted differentiation assays and western blot analysis with signal transduction inhibitors and found that vitamin B(12) did not promote PC12 cell differentiation in the presence of K252a or U0126 inhibitors. These results suggest that vitamin B(12 )stimulates PC12 cell differentiation through enhancement of the mitogen-activated protein kinase signal transduction pathway, which is also induced by nerve growth factor. Thus, vitamin B(12) may be a good candidate for treatment of neurodegenerative diseases such as Alzheimer's disease.