Proteomic profiling of Camelus dromedarius blood leukocytes using protein sequence database searches and de novo peptide sequencing

There is a lack of studies on the crude leukocyte proteome of camels. Therefore, we hypothesized that camel leukocytes could be a source of bioactive peptides that have not been studied before. Here, we present the first comprehensive proteomic analysis of dromedary camel crude leukocyte-derived polypeptides (CLDP) using both protein sequence database searches (PSD) and de novo peptide sequencing (DPS) to improve peptide identification and coverage. The crude protein was extracted and analyzed by LC-MS/MS, followed by identification of protein and peptide sequences through PSD and DPS. PSD identified 120 proteins based on the Camelus dromedarius and Sus scrofa databases, while DPS identified a total of 830 peptides with an average local confidence (ALC) of 95% or higher. Gene Ontology (GO) annotation and KEGG analysis highlighted terms associated with stress adaptation, extracellular signaling, and immune response. However, DPS exhibited a broader and more pronounced enrichment trend, particularly in relation to the immune system.