The structure-function relationship of human bleomycin hydrolase: mutation of a cysteine protease into a serine protease

Human bleomycin hydrolase (hBH) catalyzes deamidation of the anticancer drug, bleomycins (BLM). This enzyme is involved in BLM detoxification and drug resistance. Herein, we report the putative BLM-binding site and catalytic mechanism of hBH. The crystal structures and biochemical studies support that hBH cleaves its C-terminal residue without significant preference for the type of amino acids, and therefore can accordingly accommodate the β-aminoalanine amide moiety of BLM for deamidation. Interestingly, hBH is capable of switching from a cysteine protease to a serine protease that is unable to cleave the secondary amide of hBH C-terminus but reacts with the primary amide of BLMs.

Bleomycin Can Cleave an Oncogenic Noncoding RNA

Noncoding RNAs are pervasive in cells and contribute to diseases such as cancer. A question in biomedical research is whether noncoding RNAs are targets of medicines. Bleomycin is a natural product that cleaves DNA; however, it is known to cleave RNA in vitro. Herein, an in-depth analysis of the RNA cleavage preferences of bleomycin A5 is presented. Bleomycin A5 prefers to cleave RNAs with stretches of AU base pairs. Based on these preferences and bioinformatic analysis, the microRNA-10b hairpin precursor was identified as a potential substrate for bleomycin A5. Both in vitro and cellular experiments demonstrated cleavage. Importantly, chemical cleavage by bleomycin A5 in the microRNA-10b hairpin precursors occurred near the Drosha and Dicer enzymatic processing sites and led to destruction of the microRNA. Evidently, oncogenic noncoding RNAs can be considered targets of cancer medicines and might elicit their pharmacological effects by targeting noncoding RNA.

MCRs reshaped into a switchable microwave-assisted protocol toward 5-aminoimidazoles and dihydrotriazines

A tunable microwave-assisted protocol for the synthesis of two biologically relevant families of heterocycles has been designed. Via a simple switch of reaction conditions, the same starting materials can be engaged in either an improved synthesis of the dihydrotriazine scaffold or a novel, first-in-class MCR to render the challenging 5-aminoimidazole nucleus in a single step. An additional first in class MCR is also reported utilizing guanidines to afford 2,5-aminoimidazoles.

Malyngamide X: The First (7R)-Lyngbic Acid that Connects to a New Tripeptide Backbone from the Thai Sea HareBursatella leachii

Malyngamide X (1), the first (7R)-lyngbic acid connected to a new tripeptide backbone, was isolated from the Thai sea hare Bursatella leachii. The gross structure of 1 was established on the basis of 1D and 2D NMR and mass spectroscopic data. Combination of the NMR spectroscopic experiments with alpha-methoxy-alpha-(trifluoromethyl)phenylacetic acid esters, 2,2,2-trifluoro-1-(9-anthryl)ethanol chiral solvating agent, and molecular mechanics of 1 and the synthetic molecular fragments allowed us to determine the absolute stereochemistry of all six stereogenic centers without hydrolytic degradation of the compound. Compound 1 displayed moderate cytotoxic, antitubercular, and antimalarial properties.

Synthesis of 4-Deoxy-l-(and d-)hexoses from Chiral Noncarbohydrate Building Blocks

4-Deoxy-l-hexoses were synthesized starting from our previously reported reagent 1 and (R)-benzyl glycidyl ether, which led in few steps to a substituted dihydropyran 6. The stereocontrolled hydroxylation of the latter afforded the corresponding 4-deoxy-l-hexoses 7a, 9, and 11. The same procedure, starting from (S)-benzyl glycidyl ether, enabled the preparation of their d-series enantiomers.