Derivatives of epinephrine, norepinephrine, octopamine and histamine formed by homogenates of Trichostrongylus colubriformis, a nematode parasite of ruminants

1. Radiolabeled epinephrine, norepinephrine, octopamine and histamine were introduced into homogenates of mixed sexes of the nematode Trichostrongylus colubriformis and the labeled derivatives formed during incubation were identified by HPLC. Vanillylmandelic acid (VMA), 4-hydroxy-3-methoxyphenyl glycol (HMPG) and metanephrine were formed from epinephrine. 2. VMA, HMPG and normetanephrine were produced from norepinephrine. 3. Octopamine was converted into norepinephrine, synephrine and epinephrine. 4. Imidazole-4-acetic acid, 1,4-methylimidazole acetic acid and acetylhistamine were formed from histamine. 5. Inhibitors of monoamine oxidase, catechol-O-methyltransferase and phenylethanolamine-N-methyltransferase were tested for their effects on the formation of certain of these derivatives, and the results suggested that these enzymes were active in the homogenate.     

Substrate recognition by three family 13 yeast alpha-glucosidases.

Important hydrogen bonding interactions between substrate OH-groups in yeast alpha-glucosidases and oligo-1,6-glucosidase from glycoside hydrolase family 13 have been identified by measuring the rates of hydrolysis of methyl alpha-isomaltoside and its seven monodeoxygenated analogs. The transition-state stabilization energy, DeltaDeltaG, contributed by the individual OH-groups was calculated from the activities for the parent and the deoxy analogs, respectively, according to DeltaDeltaG = -RT ln[(Vmax/Km)analog/(Vmax/Km)parent]. This analysis of the energetics gave DeltaDeltaG values for all three enzymes ranging from 16.1 to 24.0 kJ.mol-1 for OH-2', -3', -4', and -6', i.e. the OH-groups of the nonreducing sugar ring. These OH-groups interact with enzyme via charged hydrogen bonds. In contrast, OH-2 and -3 of the reducing sugar contribute to transition-state stabilization, by 5.8 and 4.1 kJ.mol-1, respectively, suggesting that these groups participate in neutral hydrogen bonds. The OH-4 group is found to be unimportant in this respect and very little or no contribution is indicated for all OH-groups of the reducing-end ring of the two alpha-glucosidases, probably reflecting their exposure to bulk solvent. The stereochemical course of hydrolysis by these three members of the retaining family 13 was confirmed by directly monitoring isomaltose hydrolysis using 1H NMR spectroscopy. Kinetic analysis of the hydrolysis of methyl 6-S-ethyl-alpha-isomaltoside and its 6-R-diastereoisomer indicates that alpha-glucosidase has 200-fold higher specificity for the S-isomer. Substrate molecular recognition by these alpha-glucosidases are compared to earlier findings for the inverting, exo-acting glucoamylase from Aspergillus niger and a retaining alpha-glucosidase of glycoside hydrolase family 31, respectively.     

A novel approach to evaluate ELISA antibody coverage of host cell proteins—combining ELISA-based immunocapture and mass spectrometry

Monitoring host cell proteins (HCPs) is one of the most important analytical requirements in production of recombinant biopharmaceuticals to ensure product purity and patient safety. Enzyme-linked immunosorbent assay (ELISA) is the standard method for monitoring HCP clearance. It is important to validate that the critical reagent of an ELISA, the HCP antibody, covers a broad spectrum of the HCPs potentially present in the purified drug substance. Current coverage methods for assessing HCP antibody coverage are based on 2D-Western blot or immunoaffinity-purification combined with 2D gel electrophoresis and have several limitations. In the present study, we present a novel coverage method combining ELISA-based immunocapture with protein identification by liquid chromatography–tandem mass spectrometry (LC–MS/MS): ELISA-MS. ELISA-MS is used to accurately determine HCP coverage of an early process sample by three commercially available anti-Escherichia coli HCP antibodies, evading the limitations of current methods for coverage analysis, and taking advantage of the benefits of MS analysis. The results obtained comprise a list of individual HCPs covered by each HCP antibody. The novel method shows high sensitivity, high reproducibility, and enables tight control of nonspecific binding through inclusion of a species-specific isotype control antibody. We propose that ELISA-MS will be a valuable supplement to existing coverage methods or even a replacement. ELISA-MS will increase the possibility of selecting the best HCP ELISA, thus improving HCP surveillance and resulting in a final HCP profile with the lowest achievable risk. Overall, this will be beneficial to both the pharmaceutical industry and patient safety.