{"id":6010,"date":"2026-10-19T09:48:22","date_gmt":"2026-10-19T09:48:22","guid":{"rendered":"https:\/\/phd.hi.is\/doktorsvorn\/doktorsvorn-i-matvaelafraedi-gunnar-birgir-sandholt\/"},"modified":"2026-10-19T09:48:22","modified_gmt":"2026-10-19T09:48:22","slug":"doktorsvorn-i-matvaelafraedi-gunnar-birgir-sandholt","status":"publish","type":"phd_defence","link":"https:\/\/phd.hi.is\/en\/doktorsvorn\/doktorsvorn-i-matvaelafraedi-gunnar-birgir-sandholt\/","title":{"rendered":"Doktorsv\u00f6rn \u00ed matv\u00e6lafr\u00e6\u00f0i – Gunnar Birgir Sandholt"},"content":{"rendered":"
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F\u00f6studaginn 15. febr\u00faar ver Gunnar Birgir Sandholt doktorsritger\u00f0 s\u00edna \u00ed matv\u00e6lafr\u00e6\u00f0i vi\u00f0 Matv\u00e6la- og n\u00e6ringarfr\u00e6\u00f0ideild H\u00e1sk\u00f3la \u00cdslands. Ritger\u00f0in ber heiti\u00f0: Tryps\u00edn \u00far Atlantshafs\u00feorski (Gadus morhua) \u2013 margbreytileiki \u00eds\u00f3ens\u00edma og veiruhemjandi virkni. Atlantic cod (Gadus morhua) trypsin \u2013 isoenzyme diversity and antiviral activity.<\/p>\n

Andm\u00e6lendur eru dr. Turid Rustad, pr\u00f3fessor vi\u00f0 NTNU \u00ed Noregi, og dr. Gu\u00f0mundur \u00d3li Hreggvi\u00f0sson, pr\u00f3fessor vi\u00f0\u00a0 L\u00edf- og umhverfisv\u00edsindadeild H\u00e1sk\u00f3la \u00cdslands.<\/p>\n

Lei\u00f0beinendur og umsj\u00f3narkennarar voru dr. \u00c1g\u00fasta Gu\u00f0mundsd\u00f3ttir, pr\u00f3fessor emeritus vi\u00f0 Matv\u00e6la-og n\u00e6ringarfr\u00e6\u00f0ideild, og dr. Bjarki Stef\u00e1nsson, hj\u00e1 l\u00edft\u00e6knifyrirt\u00e6kinu Zymetech.\u00a0 Auk \u00feeirra s\u00e1tu \u00ed doktorsnefnd dr. \u00de\u00f3rhallur I. Halld\u00f3rsson, pr\u00f3fessor vi\u00f0 Matv\u00e6la-og n\u00e6ringarfr\u00e6\u00f0ideild, dr. Arthur L\u00f6ve, pr\u00f3fessor vi\u00f0 L\u00e6knadeild, og dr. Reynir Scheving, s\u00e9rfr\u00e6\u00f0ingur hj\u00e1 Zymetech.<\/p>\n

\u00d3l\u00f6f Gu\u00f0n\u00fd Geirsd\u00f3ttir, d\u00f3sent og forseti Matv\u00e6la- og n\u00e6ringarfr\u00e6\u00f0ideildar, stj\u00f3rnar ath\u00f6fninni sem fer fram \u00ed H\u00e1t\u00ed\u00f0asal H\u00e1sk\u00f3la\u00a0 \u00cdslands og hefst kl. 13:00.<\/p>\n

\u00c1grip af ranns\u00f3kn <\/strong><\/p>\n

Markmi\u00f0 doktorsverkefnisins var a\u00f0 einangra og skilgreina mismunandi tryps\u00edn \u00eds\u00f3ens\u00edm \u00far bensamid\u00edn hreinsa\u00f0ri tryps\u00ednbl\u00f6ndu. Jafnframt a\u00f0 rannsaka hvort \u00feorskatryps\u00edn geti \u00f3virkja\u00f0 veirur sem valda s\u00fdkingum \u00ed efri \u00f6ndunarvegi.<\/p>\n

Byrja\u00f0 var \u00e1 a\u00f0 greina tryps\u00edn is\u00f3ens\u00edmin X og ZT \u00far benzamidine hreinsa\u00f0ri tryps\u00ednbl\u00f6ndu. St\u00f6\u00f0ugleiki \u00feeirra gagnvart breytingum \u00e1 hitastigi, s\u00fdrustigi og ens\u00edmhindrum var rannsaka\u00f0ur og borinn saman vi\u00f0 \u00e1\u00f0ur \u00feekkt tryps\u00edn I. Notu\u00f0 var n\u00fdst\u00e1rleg a\u00f0fer\u00f0, s\u00e9rt\u00e6k hvarfefnam\u00e6ling me\u00f0 massagreiningu, til a\u00f0 bera saman s\u00e9rh\u00e6fni tryps\u00edn \u00eds\u00f3ens\u00edma I og ZT en ni\u00f0urst\u00f6\u00f0urnar leiddu \u00ed lj\u00f3s umtalsver\u00f0an mun. \u00de\u00e1 var einnig nokkur breytileiki \u00ed bindingu vi\u00f0 ens\u00edmhindra \u00e1 milli tryps\u00edn \u00eds\u00f3ens\u00edma I, X og ZT.<\/p>\n

Eiginleiki tryps\u00ednbl\u00f6ndunnar til a\u00f0 \u00f3virkja veirur, sem s\u00fdkja frumur \u00ed efri \u00f6ndunarvegi, var rannsaka\u00f0ur. Ni\u00f0urst\u00f6\u00f0urnar leiddu \u00ed lj\u00f3s a\u00f0 tryps\u00ednblandan \u00f3virkjar rhinoveiru 1A og coxsackieveiru B. Me\u00f0h\u00f6ndlun me\u00f0 l\u00e1gum styrk af \u00feorskatryps\u00edni leiddi einnig til \u00f3virkjunar coronaveiru. S\u00fdnt var fram \u00e1 \u00feennan eiginleika \u00feorskatryps\u00edns me\u00f0 notkun Renilla luciferase m\u00e6lingar \u00e1samt m\u00e6lingum \u00e1 l\u00edfv\u00e6nleika veirume\u00f0h\u00f6ndla\u00f0ra fruma. \u00de\u00e1 var s\u00fdnt fram \u00e1 getu \u00feorskatryps\u00ednbl\u00f6ndunnar vi\u00f0 a\u00f0 klj\u00fafa coronaveiru spike pr\u00f3tein me\u00f0 Western blot a\u00f0fer\u00f0. H\u00e6fni trypsin \u00eds\u00f3ens\u00edma I og ZT vi\u00f0 a\u00f0 brj\u00f3ta ni\u00f0ur SARS spike pr\u00f3tein var samb\u00e6rileg, byggt \u00e1 SDS-PAGE greiningu.<\/p>\n

Ni\u00f0urst\u00f6\u00f0urnar s\u00fdna a\u00f0 \u00feorskatryps\u00edn \u00eds\u00f3ens\u00edm X og ZT hafa \u00e1hugaver\u00f0a eiginleika sem eru fr\u00e1brug\u00f0nir eiginleikum tryps\u00edns I, sem \u00e1\u00f0ur hefur veri\u00f0 skilgreint. Einnig var s\u00fdnt fram \u00e1 a\u00f0 \u00feorskatryps\u00edn getur \u00f3virkja\u00f0 mismunandi \u00f6ndunarf\u00e6raveirur og broti\u00f0 ni\u00f0ur spike pr\u00f3tein sem finnast \u00e1 yfirbor\u00f0i coronaveira, \u00fear me\u00f0 tali\u00f0 SARS veira.<\/p>\n

Abstract<\/strong><\/p>\n

The aim of the thesis work was to identify and characterise different trypsin isoenzymes from a benzamidine purified Atlantic cod (Gadus morhua) trypsin isolate. Also, to test the ability of cod trypsin in deactivating upper respiratory tract viruses.<\/p>\n

Initially, the stability of the trypsin isoenzymes I, X and ZT in terms of temperature and pH was characterised along with their sensitivity to various inhibitors. Multiplex substrate profiling by mass spectrometry of trypsin ZT compared to trypsin I revealed a difference in substrate specificity between the two trypsin isoenzymes. Furthermore, trypsin X, I and ZT showed a difference in sensitivity to inhibitors.<\/p>\n

The deactivation potential of the cod trypsin isolate towards several upper respiratory viruses was tested. The results demonstrated that cod trypsin can deactivate rhinovirus 1A and coxsackievirus B. Furthermore, cod trypsin deactivated coronavirus. This was shown using Renilla luciferase assay and confirmed with a viability test. Furthermore, cod trypsin degraded recombinant coronavirus spike protein based on Western blot analysis. The SARS coronavirus spike protein was treated with cod trypsin isoenzymes I and ZT to test the contribution of each isoenzyme in the cleavage. Both isoenzymes cleaved the SARS coronavirus spike protein at low trypsin concentrations.<\/p>\n

In conclusion, the results show that cod trypsin X and cod trypsin ZT have interesting characteristics that differ from the previously characterised cod trypsin I. Cod trypsin was also shown to deactivate different viruses and to cleave recombinant coronavirus spike proteins.<\/p>\n

Um doktorsefni\u00f0 \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 <\/strong><\/p>\n

Gunnar Birgir Sandholt er f\u00e6ddur \u00ed Reykjav\u00edk \u00e1ri\u00f0 1983. Hann lauk st\u00fadentspr\u00f3fi af n\u00e1tt\u00farufr\u00e6\u00f0ibraut Fj\u00f6lbrautask\u00f3lans \u00ed Gar\u00f0ab\u00e6 \u00e1ri\u00f0 2004, BS-pr\u00f3fi \u00ed matv\u00e6lafr\u00e6\u00f0i fr\u00e1 H\u00e1sk\u00f3la \u00cdslands \u00e1ri\u00f0 2010 og MS-pr\u00f3fi \u00ed efnafr\u00e6\u00f0i fr\u00e1 sama sk\u00f3la \u00e1ri\u00f0 2012. Me\u00f0fram doktorsn\u00e1minu hefur Gunnar starfa\u00f0 vi\u00f0 ranns\u00f3knir hj\u00e1 l\u00edft\u00e6knifyrirt\u00e6kinu Zymetech \u00e1samt stundakennslu vi\u00f0 H\u00e1sk\u00f3la \u00cdslands. Foreldrar Gunnars eru G\u00edsl\u00edna G. Sigurgunnarsd\u00f3ttir og Egill Sandholt. Gunnar er \u00ed samb\u00fa\u00f0 me\u00f0 Sigr\u00fanu Ag\u00f6thu \u00c1rnad\u00f3ttir og b\u00faa \u00feau \u00ed Reykjav\u00edk \u00e1samt b\u00f6rnum hennar El\u00edsabetu Erlu og Alex\u00f6ndru \u00c1rn\u00fd.<\/p>\n<\/div><\/div>","protected":false},"featured_media":1246,"template":"","meta":{"site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"default","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","ast-disable-related-posts":"","theme-transparent-header-meta":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"default","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"ast-content-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"_phd_date_start":"2019-02-15T13:00:00+00:00","_phd_date_end":"2019-02-15T16:00:00+00:00","_phd_location":"A\u00f0albygging H\u00e1t\u00ed\u00f0asalur H\u00e1sk\u00f3la \u00cdslands","_phd_admission":"A\u00f0gangur \u00f3keypis","_phd_thesis_title":"Tryps\u00edn \u00far Atlantshafs\u00feorski (Gadus morhua) \u2013 margbreytileiki \u00eds\u00f3ens\u00edma og veiruhemjandi virkni. 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