# Molecular Basis of Dipeptide Recognition in Drosophila melanogaster Angiotensin I-Converting Enzyme Homologue, AnCE

## TL;DR

This study explores how dipeptides bind to AnCE, a fruit fly enzyme similar to human ACE, to help design better, targeted inhibitors for treating diseases.

## Contribution

The study identifies specific dipeptide binding sites and residues in AnCE that could guide the development of domain-specific ACE inhibitors.

## Key findings

- Dipeptides bind AnCE at non-prime and prime subsites with hydrophobic residues and tryptophan showing high affinity.
- A key pocket in the S2′ subsite influences binding orientation and may explain ACE's dipeptidyl carboxypeptidase activity.
- Dipeptides found in functional foods could serve as natural, diet-based ACE inhibitors.

## Abstract

Human angiotensin-I-converting enzyme (ACE) is involved in vasoregulation, inflammation, and neurodegenerative disorders. The enzyme is formed of two domains; the C-domain (cACE) is primarily involved in blood pressure regulation, whereas the N-domain (nACE) is strongly linked to fibrosis; hence, designing domain-specific inhibitors could make a difference between treating one condition without having a negative effect on another. AnCE (a close homologue of ACE) is derived from Drosophila melanogaster and has a high similarity specifically to cACE. Due to high similarity and ease of crystallisation, AnCE has been chosen as a model protein for ACE studies and for the design of ACE inhibitors. In this study, enzyme kinetic assays and X-ray crystallography techniques revealed the significance of using dipeptides as selective inhibitors for AnCE and how this knowledge could be applied to cACE and nACE. All the dipeptides tested in this study were shown to bind AnCE in two distinct locations, i.e., the non-prime and prime subsites. It was found that a hydrophobic residue at the S1 and S1′ subsites, with a tryptophan at the S2 and S2′ subsites, showed highest affinity towards AnCE. It was also observed that a key pocket within the S2′ subsite had a major influence on the binding orientation within the prime subsites and could potentially explain ACE’s dipeptidyl carboxypeptidase activity. Importantly these dipeptides are found in functional foods, making them potentially available from diets. Knowledge of the dipeptide binding presented here could aid in the development of ACE domain-specific inhibitors.