A Study of Bovine Βeta Lactoglobulin: Its Catalytic Activity and Role in The Biosynthesis Of Cycloretinal, A Key Lipofuscin

The accumulation of lipofuscins such as all-trans retinal dimer/cycloretinal in the retina may contribute to the progression of age-related macular degeneration (AMD). While the biosynthesis of cycloretinal is not fully understood, it has been shown that the milk protein β-lactoglobulin (BLG) can promote the cyclodimerization of all-trans retinal to cycloretinal both in vitro and in vivo. To further our understanding of this cyclodimerization, we have used site-directed mutagenesis of BLG as well as mass spectrometric analysis with substrate analogs to demonstrate that lysine residues play a key role in catalysis. It is shown that catalytic activity necessitates the presence of a physical binding site and cannot be mediated by a peptide chain. We also report that BLG is a promiscuous enzyme (a feature common to enzymes with a hydrophobic binding site and an active site lysine) that can catalyze the retroaldol cleavage of α, β unsaturated aldehydes. Retroaldolase activity was seen to be most effective on substrates with phenyl or napththyl side-chains. While the fluorescence images reported in this dissertation suggest that BLG may not be crossing into the retina to be the major protein responsible for cycloretinal biosynthesis, it might be possible that the blood-retina barrier becomes less coherent with age. These studies provide insight into the mechanism of the cyclodimerization process and provide a model system for biocatalysis and biosynthesis of cycloretinal in vivo. In the long term, these studies may pave the way for drug development and inhibitor design as an early treatment regimen for AMD.

Name thesis:degree_name

Doctor of Philosophy

Level thesis:degree_level

Doctoral

Discipline thesis:degree_discipline

Chemistry

Grantor

Texas A&M University

Year dc:date.issued

2018

Author dc:creator

• Gowda, Vishruth

Advisor dc:contributor.advisor

• Watanabe, Coran MH

Committee members dc:contributor.committeemember

• Begley, Tadhg P
• Siegele, Deborah A
• Barondeau, David P

• Lipofuscin
• cycloretinal
• beta lactoglobulin
• BLG
• retroaldolase
• blood-borne BLG
• age-related macular degeneration
• AMD

Language dc:language.iso

en

Handle dc:identifier.uri

https://hdl.handle.net/1969.1/188896

OAI record oai:identifier

https://oaktrust.library.tamu.edu/server/oai/request?verb=GetRecord&metadataPrefix=dim&identifier=oai%3Aoaktrust.library.tamu.edu%3A1969.1%2F188896