Biokatalitička svojstva halogenhidrin-dehalogenaza skupine B u reakcijama nukleofilnog otvaranja epoksida

doctoral thesis

• Title (english): Biocatalytic properties of group B halohydrin dehalogenases in nucleophilic ring-opening reactions of epoxides
• Author: Emina Mehić
• Mentor: Maja Majerić-Elenkov (mentor)
• Mentor: Zvjezdana Findrik Blažević (mentor)
• Committee member: Martina Sudar (predsjednik povjerenstva)
• Committee member: Silvana Raić-Malić (član povjerenstva)
• Committee member: Srećko Kirin (član povjerenstva)
• Granter: University of Zagreb; Faculty of Chemical Engineering and Technology; Zagreb
• Defense date and country: 2023-02-24, Croatia
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Chemistry; Organic Chemistry
• Universal decimal classification (UDC): 54 - Chemistry. Crystallography. Mineralogy

Abstract

Halogenhidrin-dehalogenaze (HHDH) su enzimi koji imaju sposobnost uvođenja novih funkcionalnih skupina u molekulu, kataliziranjem reakcije otvaranja epoksida s različitim nukleofilima. Aktivno mjesto enzima može primiti više različitih neprirodnih nukleofila poput azida, cijanida i nitrita, zbog čega su enzimi privukli pažnju sintetske organske kemije. Njihova enantioselektivnost ovisi o strukturi supstrata, te često nije dovoljno visoka za sintetsku primjenu. Enzim HheB2 iz grupe B u prethodnim istraživanjima testiran je na relativno malom broju supstrata gdje je pokazao nisku enantioselektivnost, te je dugi niz godina ostao zanemaren u biokatalitičkim istraživanjima. U okviru ovog rada provedeno je opsežno ispitivanje dva divlja tipa HHDH iz skupine B: HheB iz Croynebacterium sp. soj N-1074 i HheB2 iz Mycobacterium sp. soj GP1 na nizu supstrata i nukleofila. Otkriveno je nekoliko visoko enantioselektivnih reakcija (E > 200), gdje je HheB pokazao bolju enantioselektivnost i aktivnost prema većem broju strukturno različitih supstrata u usporedbi s HheB2. Ova dva enzima dijele visoku homologiju sekvence i razlikuju se u samo četiri aminokiseline (F36I, T120A, C124Y, H125Q). Ispitivanjem mutanata HheB2 s modificiranim pojedinačnim aminokiselinama utvrđene su aminokiseline ključne za veću enantioselektivnost HheB u odnosu na HheB2. Eksperimentalni rezultati potvrđeni su i dodatno pojašnjeni računalnim analizama. Zbog izuzetne selektivnosti i aktivnosti B grupa HHDH nameće se kao odličan katalizator za sintezu velikih tercijarnih alkohola. Ispitivanjem različitih nukleofila prikazana je mogućnost sinteze enantiomerno čistih azido-alkohola i oksazolidinona, a kinetičkim mjerenjima određen je stupanj inhibicije enzima prihvaćenim nukleofilma.

Abstract (english)

Halohydrin dehalogenases (HHDH) have the ability to introduce new functionalities into the molecule through the ring-opening reactions of epoxides with different nucleophiles. These enzymes draw the attention of synthetic chemistry due to their ability to accept unnatural nucleophiles such as azide, cyanide and nitrite ions. The enantioselectivity of HHDHs is substrate-dependent and not always sufficient for synthetic applications. HheB2 from B group of HHDHs has been neglected in the biocatalytic research due to the low enantioselectivity observed on a relatively small number of tested substrates. In this work, extensive screening of substrates and nucleophiles was carried out on two B wild-type HHDHs: HheB2 from Mycobacterium sp. GP1 and HheB from Corynebacterium sp. N-1074. Several highly enantioselective reactions were discovered (E > 200), with HheB showing higher enantioselectivity and activity towards larger panel of substrates compared to HheB2. These two enzymes share high sequence homology and differ by only four amino acids (F36I, T120A, C124Y, H125Q). HheB2 mutants with individual amino acids replacement are examined to determine key residues. Experimental results were confirmed and further clarified by computer analysis. Due to remarkable activity and enantioselectivity, B-group HHDHs emerged as a catalyst of choice for the synthesis of bulky tertiary alcohols. Nucleophile screening showed possibility for the synthesis of enantiomerically pure azido alcohols and oxazolidinones. Kinetic measurements were used to determine enzyme inhibition by accepted nucleophiles.

• Keywords: biokataliza; enantioselektivnost; epoksidi; HHDH; kinetička mjerenja; kinetička rezolucija; nukleofili
• Keywords (english): biocatalysis; enantioselectivity; epoxides; HHDH; kinetic measurements; kinetic resolution; nucleophiles
• Language: croatian
• URN:NBN: urn:nbn:hr:149:333636
• Promotion: 2023
• Project: Number: KK.01.1.1.04.0013; Title: Inovativna rješenja u katalitičkim proizvodnim procesima za potrebe farmaceutske industrije; Title: Innovative solutions in catalytic processes in the pharmaceutical industry; Acronym: CAT PHARMA; Leader: Srećko Kirin; Jurisdiction: eu; Funder: EC; Funding stream: EFRR
• Study programme: Title: Chemical Engineering and Applied Chemistry - Doctoral course; Study programme type: university; Study level: postgraduate; Academic / professional title: doktor/doktorica znanosti u području prirodnih znanosti (doktor/doktorica znanosti u području prirodnih znanosti)
• Type of resource: Text
• Extent: 110 str. ; 30 cm
• File origin: Born digital
• Access conditions: Open access
• Created on: 2023-03-21 13:49:35