Enzymatic oxidation of 5-hydroxymethylfurfural (HMF) and its oxidized derivatives was studied using three fungal enzymes: wild-type aryl alcohol oxidase (AAO) from three fungal species, wild-type peroxygenase from Agrocybe aegerita (AaeUPO), and recombinant galactose oxidase (GAO). The effect of pH on different reaction steps was evaluated and apparent kinetic data (Michaelis-Menten constants, ...

A new procedure has been described for the isolation and purification of ascorbate oxidase from green zucchini squash (Cucurbita pepo meduttosa). The new purification method achieves a more than ZOO-fold purification with about a 14% recovery of the total activity present in the crude juice. The purified enzyme preparations have been found to be homogeneous by the criteria of ultracentrifugal a...

We previously demonstrated that Streptococcus oligofermentans suppressed the growth of Streptococcus mutans, the primary cariogenic pathogen, by producing hydrogen peroxide (H(2)O(2)) through lactate oxidase activity. In this study, we found that the lox mutant of S. oligofermentans regained the inhibition while growing on peptone-rich plates. Further studies demonstrated that the H(2)O(2) prod...

The function of the apoplastic enzyme ascorbate oxidase (AO) was investigated in tobacco (Nicotiana tabacum). The abundance of AO mRNA was up-regulated by light. Cytosolic ascorbate peroxidase (APX1) transcripts were also highest in the light. In contrast, L-galactono-gamma-lactone dehydrogenase, stromal APX, and thylakoid APX transcripts remained constant over the day/night cycle. Salicylic ac...

Glutathione dehydrogenase (EC 1.8.5.1) was partially purified from pea shoots. The pH optimum was 7.6. The K(m) values for GSH and dehydroascorbate were 4.4 and 0.44 millimolar, respectively. The enzyme was inhibited by iodoacetate and CuSO(4) but not significantly by ZnCl(2) or NaN(3). Part of the total enzyme activity was associated with isolated chloroplasts.Illuminated ruptured chloroplasts...

Ascorbic acid (vitamin C) is an enzyme co-factor in eukaryotes that also plays a critical role in protecting photosynthetic eukaryotes against damaging reactive oxygen species derived from the chloroplast. Many animal lineages, including primates, have become ascorbate auxotrophs due to the loss of the terminal enzyme in their biosynthetic pathway, L-gulonolactone oxidase (GULO). The alternativ...

The aim of this work is to develop a method for ascorbic acid determination in some fruit juices, by using an ascorbate oxidase-based amperometric enzyme electrode. The enzyme was immobilized on a nylon (Biodyne A) membrane by glutaraldehyde linking. The enzyme-membrane was consecutively attached to the polyethylene membrane of a Clark oxygen electrode, which functioned as transducer. The analy...

Au@Pt nanorods were prepared by growing platinum nanodots on gold nanorods. Using electron spin resonance (ESR), we determined that the mechanisms for oxidation of ascorbic acid (AA) by Au@Pt nanorods and ascorbic acid oxidase (AAO) were kinetically similar and yielded similar products. In addition we observed that Au@Pt nanorods were stable with respect to temperature and pH. Using UV-VIS spec...

Rebeccamycin, a member of the tryptophan-derived indolocarbazole family, is produced by Lechevalieria aerocolonigenes ATCC 39243. The biosynthetic pathway that specifies biosynthesis of this important metabolite is comprised of 11 genes spanning 18 kb of DNA. A presumed early enzyme involved in elaboration of the rebeccamycin aglycone is encoded by rebO, located at the left-hand region of the r...

Glucose in the cerebrospinal fluid (CSF) of neonates, as measured with a kinetic glucose oxidase/peroxidase procedure, was sometimes very low. When these samples were stored at 4 degrees C and subsequently re-analyzed, or if the samples were analyzed at any time after receipt by using a glucose dehydrogenase assay, the values were much higher. We found that the discrepancies in the values were ...