Recent developments in chemical conjugation strategies targeting native amino acids in proteins and their applications in antibody-drug conjugates.

Many fields in chemical biology and synthetic biology require effective bioconjugation methods to achieve their desired functions and activities. Among such biomolecule conjugates, antibody-drug conjugates (ADCs) need a linker that provides a stable linkage between cytotoxic drugs and antibodies, whilst conjugating in a biologically benign, fast and selective fashion. This review focuses on how the development of novel organic synthesis can solve the problems of traditional linker technology.

Bacteroides thetaiotaomicron VPI-5482 glycoside hydrolase family 66 homolog catalyzes dextranolytic and cyclization reactions.

Bacteroides thetaiotaomicron VPI-5482 harbors a gene encoding a putative cycloisomaltooligosaccharide glucanotransferase (BT3087) belonging to glycoside hydrolase family 66. The goal of the present study was to characterize the catalytic properties of this enzyme. Therefore, we expressed BT3087 (recombinant endo-dextranase from Bacteroides thetaiotaomicron VPI-5482) in Escherichia coli and determined that recombinant endo-dextranase from Bacteroides thetaiotaomicron VPI-5482 preferentially synthesized isomaltotetraose and isomaltooligosaccharides (degree of polymerization > 4) from dextran.

A novel metabolic pathway for glucose production mediated by α-glucosidase-catalyzed conversion of 1,5-anhydrofructose.

α-Glucosidase is in the glycoside hydrolase family 13 (13AG) and 31 (31AG). Only 31AGs can hydrate the D-glucal double bond to form α-2-deoxyglucose. Because 1,5-anhydrofructose (AF), having a 2-OH group, mimics the oxocarbenium ion transition state, AF may be a substrate for α-glucosidases.

Novel dextranase catalyzing cycloisomaltooligosaccharide formation and identification of catalytic amino acids and their functions using chemical rescue approach.

A novel endodextranase from Paenibacillus sp. (Paenibacillus sp. dextranase; PsDex) was found to mainly produce isomaltotetraose and small amounts of cycloisomaltooligosaccharides (CIs) with a degree of polymerization of 7-14 from dextran.

Truncation of N- and C-terminal regions of Streptococcus mutans dextranase enhances catalytic activity.

Multiple forms of native and recombinant endo-dextranases (Dexs) of the glycoside hydrolase family (GH) 66 exist. The GH 66 Dex gene from Streptococcus mutans ATCC 25175 (SmDex) was expressed in Escherichia coli. The recombinant full-size (95.

A survey of respirators usage for airborne chemicals in Korea.

A questionnaire survey was undertaken to identify the current status of respirator usage in manufacturing work environments subject to gas/vapor chemicals exposure in Korea and to suggest improvements to enhance the effectiveness of respirator usage. The number of target companies included 17 big companies, 110 small & mid-size companies, and 5 foreign companies, and the number of respondents included 601 workers and 69 persons in charge of respirators (PCR). The results explained clearly that respirator programs in practice were extremely poor in small & mid-sized companies.

The first alpha-1,3-glucosidase from bacterial origin belonging to glycoside hydrolase family 31.

Genome analysis of Lactobacillus johnsonii NCC533 has been recently completed. One of its annotated genes, lj0569, encodes the protein having the conserved domain of glycoside hydrolase family 31. Its homolog gene (ljag31) in L.

Catalytic mechanism of retaining alpha-galactosidase belonging to glycoside hydrolase family 97.

Glycoside hydrolase family 97 (GH 97) is a unique glycoside family that contains inverting and retaining glycosidases. Of these, BtGH97a (SusB) and BtGH97b (UniProtKB/TrEMBL entry Q8A6L0), derived from Bacteroides thetaiotaomicron, have been characterized as an inverting alpha-glucoside hydrolase and a retaining alpha-galactosidase, respectively. Previous studies on the three-dimensional structures of BtGH97a and site-directed mutagenesis indicated that Glu532 acts as an acid catalyst and that Glu439 and Glu508 function as the catalytic base in the inverting mechanism.

Aglycone specificity of Escherichia coli alpha-xylosidase investigated by transxylosylation.

The specificity of the aglycone-binding site of Escherichia coli alpha-xylosidase (YicI), which belongs to glycoside hydrolase family 31, was characterized by examining the enzyme's transxylosylation-catalyzing property. Acceptor specificity and regioselectivity were investigated using various sugars as acceptor substrates and alpha-xylosyl fluoride as the donor substrate. Comparison of the rate of formation of the glycosyl-enzyme intermediate and the transfer product yield using various acceptor substrates showed that glucose is the best complementary acceptor at the aglycone-binding site.