10.1021/ja0587603
The research presents an in-depth study on the biosynthesis of pipecolic acid by RapL, a lysine cyclodeaminase enzyme encoded in the rapamycin gene cluster. The main focus of the study is to validate RapL's ability to convert L-lysine to L-pipecolic acid through a cyclodeamination reaction involving redox catalysis. The researchers heterologously overexpressed and purified RapL, and conducted a series of experiments to confirm its enzymatic activity. They used L-lysine and L-[U-14C]ornithine as substrates, NAD+ as a cofactor, and analyzed the reactions using techniques such as cellulose thin layer chromatography (TLC), chiral radio-HPLC, and mass spectrometry. The study also investigated the enzyme's substrate specificity, cofactor requirements, and inhibitory properties. Additionally, the researchers used isotopically labeled substrates to dissect the mechanistic details of the cyclodeaminase reaction, confirming the loss of the R-amine and retention of the hydrogen atom at the R-carbon. The experiments provided the first in vitro characterization of a lysine cyclodeaminase and contributed to the understanding of the biosynthesis of medically important natural products like rapamycin, FK506, and FK520.
10.1021/acs.orglett.8b03386
Agnieszka Mlynarska-Cieslak et al. discusses the chemical synthesis of nicotinamide adenine dinucleotide (NAD) cap analogues designed to be less susceptible to NAD-RNA degrading enzymes. The study aims to enhance the stability of NAD-capped RNAs for further biological studies. The authors synthesized a set of NAD analogues with modifications such as O-to-S substitutions at the pyrophosphate moiety and phosphorothioate/phosphorothiolate modifications. These analogues were incorporated into RNA transcripts using in vitro transcription with T7 polymerase. The modified RNAs were then tested for their susceptibility to deNADding enzymes like DXO, NudC, and Nudt12. The results identified several analogues that showed resistance to these enzymes, particularly compounds with combined modifications like a-PS and 2'-O-methylation.