Yeast cytosine deaminase (yCD), a zinc metalloenzyme, catalyzes the hydrolytic deamination of cytosine to uracil. The enzyme is of great biomedical interest because it also catalyzes the deamination of the prodrug 5-fluorocytosine (5FC) to form the anticancer drug 5-fluorouracil (5FU). yCD/5FC is one of the most widely used enzyme/prodrug combinations for gene-directed enzyme prodrug therapy fo...

While methylcytosines serve as the fifth base encoding epigenetic information, they are also a dangerous endogenous mutagen due to their intrinsic instability. Methylcytosine undergoes spontaneous deamination, at a rate much higher than cytosine, to generate thymine. In mammals, two repair enzymes, thymine DNA glycosylase (TDG) and methyl-CpG binding domain 4 (MBD4), have evolved to counteract ...

Vertebrate genomes are characterized with CpG deficiency, particularly for GC-poor regions. The GC content-related CpG deficiency is probably caused by context-dependent deamination of methylated CpG sites. This hypothesis was examined in this study by comparing nucleotide frequencies at CpG flanking positions among invertebrate and vertebrate genomes. The finding is a transition of nucleotide ...

Activation-induced cytidine deaminase (AID) is the essential enzyme inducing the DNA cleavage required for both somatic hypermutation and class switch recombination (CSR) of the immunoglobulin gene. We originally proposed the RNA-editing model for the mechanism of DNA cleavage by AID. We obtained evidence that fulfils three requirements for CSR by this model, namely (i) AID shuttling between nu...

l-Phenylalanine ammonia-lyase (PAL) activity develops in excised bean axes after approximately 5 hours of incubation and reaches a maximum level after 14 hours of incubation. Light does not affect the development of activity, but puromycin, cycloheximide, actinomycin D, and 5-fluorouracil inhibit.During this period of incubation both d- and l-p-fluorophenylalanine stimulate fresh weight increas...

The mechanism of and possible cofactors involved in the straight deamination of histidine remain unknown. Neither pyridoxal phosphate, established as a cofactor in transamination of many amino acids, nor biotin, implicated in the straight deamination of aspart,ic acid, apparently plays a role in this reaction (1). Ichihara et al. (2) have reported low levels of histidase in the livers of rats w...

In RNA viruses, mutations occur fast and have large fitness effects. While this affords remarkable adaptability, it can also endanger viral survival due to the accumulation of deleterious mutations. How RNA viruses reconcile these two opposed facets of mutation is still unknown. Here we show that, in human immunodeficiency virus (HIV-1), spontaneous mutations are not randomly located along the ...

Recent data suggest that small differences in editing efficiency can have significant functional consequences. Here we present a fluorescent poisoned primer extension assay that is capable of distinguishing editing efficiency differences as low as 5%. For a poison-primer extension assay to be accurate, the extension product must stop at the intended base. Sometimes, however, it runs beyond. We ...

Oxidation of azafulleroids with peracids regenerated C60 depending on the N-substituents. Alkyl-substituted azafulleroids preferred the oxidation of nitrogen to afford N-oxides as possible intermediates for C60 in moderate yields. Phenyl- and tosyl-substituted azafulleroids rather allowed the oxidation at the carbon cage. Theoretical calculations predicted the order of reactivity of azafulleroi...

Using periodic DFT calculations, it is concluded that the stable radiation-induced alanine radical most probably is the result of reductive deamination and protonation of the detached amino group, yielding an NH(4)(+) ammonium ion and a negatively charged radical.