R‐hydroxynitrile lyase from the cyanogenic millipede, Chamberlinius hualienensis—A new entry to the carrier protein family Lipocalines

Abstract

We determined the X‐ray crystallographic structure of a unique hydroxynitrile lyase from the cyanogenic millipede, Chamberlinius hualienensis, and elucidated the reaction mechanism. We revealed that it belongs to the lipocalins, a family of proteins active in the transport small hydrophobic molecules. It is one of a few lipocalins with enzyme activities. This addition expands the evolutionary relationship of the enzyme to a new family of proteins.

Biocatalysis making waves in organic chemistry

“…These enzymes work with sometimes very different mechanisms, from Lewis metal-catalysed to classical acid base catalysis, and have been further developed by enzyme engineering. 40,41,44,45 Independent of the mechanism, the enzymes are typically utilised in two phase systems at low pH to suppress the undesired background reaction and ensuring high substrate loadings. 38,45 Both industrially and for laboratory purposes the biocatalytic cyanohydrin synthesis is today the standard method.…”

“…The synthesis then is a biocatalytic Henry reaction (Scheme 4). 40,41,47,48 Recent developments have focussed on even more enzymes from unusual sources such as millipedes 44,[51][52][53] and bacteria, [54][55][56] the exploration of evolutionary ancestors 57 and other methods to interconvert HNL activity with other enzyme activities, in particular hydrolase activity. 58 Reaction engineering with a special focus of the application of HNLs in flow has recently led to promising results.…”

Structural characterization of Linum usitatissimum hydroxynitrile lyase: A new cyanohydrin decomposition mechanism involving a cyano-zinc complex

“…Such proton transfer from lysinium to aspartate followed with proton extraction from substrate by the deprotonated lysine has been reported in Chua HNL. The deprotonated lysine in Chua HNL was proposed to be stabilized by the desolvation effect in the hydrophobic active site ( 41 ). The desolvation effect by placing the side chain into a specific microenvironment can significantly perturb the pK a of a nucleophile, as detected for the buried lysine ( 67 ) and glutamic acid ( 68 ) in the interior of proteins.…”

“…The toxic HCN is released as a defense compound to protect from intruders. The HNLs identified to date can be classified into seven superfamilies that include FAD-binding oxidoreductase ( Pa HNL ( 11 , 12 , 13 , 14 ), Pm HNL ( 15 ), Ps HNL ( 16 ), Ej HNL ( 17 , 18 )), α/β-hydrolase fold ( At HNL ( 19 , 20 ), Me HNL ( 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 ), Hb HNL ( 29 , 30 , 31 , 32 ), Sb HNL ( 33 , 34 , 35 ), Bm HNL ( 36 , 37 )), dimeric α+β barrel ( Pe HNL ( 38 , 39 )), lipocalin-like fold ( Chua HNL ( 6 , 40 , 41 ), Plam HNL ( 42 )), cupin ( Ac HNL ( 4 ), Psm HNL ( 5 ), Bp HNL ( 5 ), Gt HNL ( 3 )), bet-v1 like fold ( Dt HNL ( 43 )), and Zn 2+ -dependent alcohol dehydrogenase ( Lu HNL ( 44 , 45 , 46 , 47 )). Among these, one or more HNL structures have been determined in each superfamily, except for the Zn 2+ -dependent alcohol dehydrogenase superfamily.…”

A Comprehensive Overview of Novel Hydroxynitrile Lyases

“…Lys117 behaves as a base to take a proton from the -OH group of cyanohydrins, while Arg38 serves as an acid to give a proton to the CNion during the bond fission reaction, according to mutational studies. During the cyanohydrin production process, the opposite will happen (Motojima et al . 2021).…”