A Facile Method to Determine Prolidase Activity Using a Peptide-Specific Fluorometric Reaction.

Prolidase is the only enzyme capable of cleaving imidodipeptides containing C-terminal proline (Pro) or hydroxyproline and plays a crucial role in several physiological processes such as wound healing and cell proliferation. Here, we developed a new method to determine prolidase activity. This method is based on a novel fluorescence (FL) reaction selective for N-terminal glycine (Gly)-containing peptides using 3,4-dihydroxyphenylacetic acid (3,4-DHPAA). The 3,4-DHPAA can selectively react with Gly-Pro, the substrate for prolidase, and the prolidase activity is measured by monitoring the decrease in FL intensities. The prolidase activities in fibroblasts and HeLa cells were successfully measured by the proposed method. Compared with classical Chinard's method, our method does not require any caustic acids, pre-incubation to activate the enzyme, and heating for reaction with the detection reagent. The proposed method enables facile and specific measurement for biogenic prolidase activity.

Effect of manuka honey on human immunodeficiency virus type 1 reverse transcriptase activity.

Manuka honey (MkH), derived from New Zealand manuka tree (Leptospermum scoparium), is considered a therapeutic agent owing to its antibacterial, antioxidant, antifungal, antiviral, anti-inflammatory, and wound healing activities. In this study, the inhibitory effect of five honey types, including MkH, on HIV-1 RT activity was evaluated, using an RT assay colorimetric kit, according to the manufacturer's instructions with slight modifications. MkH exerted the strongest inhibitory effect in a dose-dependent manner, with a half maximal inhibitory concentration (IC50) of approximately 14.8 mg/mL. Moreover, among the MkH constituents, methylglyoxal (MGO) and 2-methoxybenzoic acid (2-MBA) were determined to possess anti-HIV-1 RT activity. MGO and 2-MBA in MkH were identified by High Performance Liquid Chromatography (HPLC) and Liquid Chromatograph - Mass Spectrometry (LC-MS/MS). The findings suggest that the inhibitory effect of MkH on the HIV-1 RT activity is mediated by multiple constituents with different physical and chemical properties.

Simultaneous assay for protease activities of hepatitis C virus and human immunodeficiency virus based on fluorescence detection.

Hepatitis C virus protease (HCV-PR) and human immunodeficiency virus protease (HIV-PR) are important for virus maturation, and thus can be used as potential target molecules for the development of antiviral drugs for the treatment of viral infections. In this study, a novel assay was developed to determine HCV-PR activity. This assay is based on a fluorogenic reaction, in which peptide fragments generated from an acetyl peptide substrate by HCV-PR can be selectively converted into a fluorescent derivative, and quantified by high-performance liquid chromatography (HPLC) with fluorescent detection. Herein, several acetyl-peptides can be used as substrates for HPLC. The application of this assay was further validated by simultaneous detection of HCV-PR and HIV-PR in a reaction mixture. The proposed method can differentiate the enzyme activities of HCV-PR and HIV-PR in a sample using their corresponding substrates. The results suggest that this assay can detect various proteases by employing set of substrate peptides under the same reaction conditions.

Facile assay of telomerase activity utilizing a DNA-detectable chemiluminogenic reagent.

Telomerase shows increased activity in most human cancers and germ line cells, but not in normal human somatic cells. We describe a novel chemiluminescence method for the facile assay of telomerase activity in human cells. The telomerase substrate was incubated with the cell lysate containing various amounts of telomerase, and then the telomerase product was amplified by the polymerase-chained reaction (PCR). The PCR products were separated from the excess substrate, primer and deoxyribonucleotide triphosphates by a centrifugal filter, which distinguished different molecular sizes. The isolated products were reacted with a DNA-detectable chemiluminogenic reagent, 3,4,5-trimethoxyphenylglyoxal. The proposed assay method gave linearity for the telomerase activity in 100 to 10000 cells (r2=0.997), and allowed the assay not only of lower activity, but also of higher activity of telomerase without the requirement of any special labeled-PCR primers in the assay system.

Sensitive liquid chromatography/tandem mass spectrometry method for the simultaneous determination of nine local anesthetic drugs.

A high-performance liquid chromatography-tandem mass spectrometry (LC/MS/MS) with electrospray ionization (ESI) procedure for the simultaneous determination of nine local anesthetic drugs (procaine, mepivacaine, lidocaine, ropivacaine, oxybuprocaine, tetracaine, bupivacaine, T-caine and dibucaine) in human serum is described. The chromatographic separation was performed on a Mightysil-RP-18 GP II column (2.0mm×150mm, particle size 5µm). The mobile phase consisted of 10mM acetic ammonium buffer (pH 5.4) and acetonitrile and was delivered at a flow rate of 0.20mL/min. The triple quadrupole mass spectrometer was operated in positive ion mode, and multiple reaction monitoring was used for drug quantification. Solid-phase extraction of the nine local anesthetic drugs added to the human serum was performed with an Oasis(®) HLB extraction cartridges column. The method was linear for the investigated drugs over the concentration range of 10-100ng/mL. The recoveries of these drugs were in the range of 81.4-144%. The standard deviation (SD) values for all analytes were <0.10 for both intraday and interday accuracy and precision. The selectivity, accuracy and precision of this method are satisfactory for clinical and forensic applications. The sensitive and selective method offers the opportunity for the simultaneous screening and quantification, for clinical and forensic purposes, of almost all local anesthetics available in Japan.

Simultaneous determination for oxicam non-steroidal anti-inflammatory drugs in human serum by liquid chromatography-tandem mass spectrometry.

A high-performance liquid chromatography-tandem mass spectrometry (LC/MS/MS) technique was developed for the simultaneous determination of five non-steroidal anti-inflammatory oxicam drugs (ampiroxicam, tenoxicam, piroxicam, meloxicam and lornoxicam) in human plasma. These five oxicam drugs and isoxicam (internal standard) were extracted from human plasma with an Oasis(®) MAX cartridge column and analysed on a Unison UK-C18 column (2.0 mm × 100 mm, 3 µm) with an acetonitrile:10mM formic ammonium buffer (pH 3.0) (50:50) mobile phase at 0.20 ml/min at 37°C. The analytes were detected using a tandem mass spectrometer, equipped with an electrospray ion source (ESI). The instrument was used in multiple-reaction-monitoring (MRM) mode. The extraction yields from a 200 µl human plasma sample (containing 10 ng of each drugs) with the Oasis(®) MAX cartridge column were 93.3-102.5%. The detection limits were 0.01-6.5 ng/ml (S/N=3). Our developed method is very useful for the simultaneous determination of five oxicam (non-steroidal anti-inflammatory) drugs in human plasma by LC/MS/MS.

Facile determination of DNA-binding nuclear factor-kappaB by chemiluminescence detection.

A simple, rapid, and sensitive method for the assay of a sequence-specific DNA-binding protein, nuclear factor-kappaB (NF-kappaB), has been developed by using a DNA-detectable chemiluminogenic reagent and a centrifugal filter that distinguishes different molecular sizes. After the formation of a complex between NF-kappaB and DNA, the unbound DNA is separated from the complex by the centrifugal filter. The amount of the bound NF-kappaB is estimated by chemiluminescence detection of the bound DNA. This detection is performed within 2 min at room temperature by the use of a chemiluminogenic reagent, 3',4',5'-trimethoxyphenylglyoxal, which selectively recognizes guanine moiety in oligonucleotides or DNAs. This method does not require any labeled probes or antibodies and can determine a concentration as low as 5 nM of DNA-binding NF-kappaB. The sensitivity is nearly the same as that of other methods such as gel shift assay using fluorescence-labeled probes and enzyme-linked immunosorbent assay. Therefore, the current method provides a convenient tool for surveying various DNA-binding proteins.