Antonia Miller (Maillard Reaction in Proteins)

The Maillard reaction is a post-translational modification of biomolecules which involves the attachment of carbonyl groups (eg sugars) to primary amines contained in the target biomolecule (eg protein) (Figure 1). Following this initial glycation step, a Schiff base adduct is formed, followed by a rearrangement to a more stable Amadori product. At this point the Amadori product can undergo a variety of reactions, such as cyclisation and fragmentation to form Advanced Glycation End products (AGEs), some of which form the basis for protein crosslinks. These non-enzymatically formed crosslinks have been implicated in the modification of structure and thus potential function of some biologically important proteins, as manifested in a number of diseases.

Figure 1: The Maillard reaction: Reaction of a sugar (eg glucose) with an amine (eg lysine from protein)

The project aims firstly to rigorously examine the contribution of particular amino acids (lysine and arginine) to this reaction, in an attempt to understand the chemical and biochemical mechanisms of the Maillard reaction and thus may shed further light on the mechanisms involved in advanced glycation end product formation.

The benefit of a better understanding of the mechanistics of the Maillard reaction is the knowledge this information will provide for inhibitor design. Inhibitor elucidation and design is a burgeoning area and a number of compounds have been identified or developed which act at a variety of points in the Maillard scheme, with a view to controlling Maillard-mediated diseases. Traditionally, chemical compounds have been used to trap Maillard reactants (such as sugars) or to break AGE crosslinks. However, a class of fungi and a class of bacteria have been isolated which produce Amadoriases.These enzymes act to cleave the Amadori product (Figure 1), forming the initial components lysine and sugar. A limited amount of work has been undertaken in terms of assessing deglycating ability employing some ambiguous circumstances. This project aimed to address this ambiguity.

Mutational studies of amadoriase I have also been performed in order to determine the residues that are involved in the catlytic mechanism of these enzymes.