Mapping of the ocular surface enzymes in healthy subjects

AbstractPurpose: This study aimed to pool identified enzymes from numerous comprehensive open‐access proteomic studies to profile and classify detected enzymes on the ocular surface (OS).Methods: Data were taken from studies that analysed tear samples of healthy subjects either collected by capillary tubes (CT (tears), n = 5) or Schirmer strips (ScS, n = 5). Enzymes were mapped using UniProt ‘enzyme class’ (EC) and Panther software. Functional analysis was done using Metascape.Results: In total, 1010 enzymes were identified from all studies which are classified as oxidoreductases (EC1, 13.4%), transferases (EC2–30.3%), hydrolases (EC 3–42.3%), lyases (EC 4–4.3%), isomerases (EC5–4.1%), ligases (EC6–4.1%), translocases (EC 7–1.4%). More isomerases (5% vs. 3.4%) and ligases (4.7% vs. 4.1%) could be identified in ScS samples. Isomerases formed 5.6% of specific enzymes detected only in ScS while no specific isomerase was found in tears. Antioxidant and antimicrobial enzymes, EC1 class, were formed by dehydrogenases 36.2%, reductases 23.3%, oxidoreductases 18.1%, peroxidases 10.3%, oxygenases 7.8% and oxidases 4.3%. Alcohol oxidoreductases (EC1.1) were the most represented subgroup of EC1 with 46 enzymes (34.3%). Of all enzymes EC2.7 (phosphotransferases), EC3.1 (esterases) and EC3.4 (peptidases) were the most represented subclasses with 156, 151, 172 enzymes, respectively. The metabolic process of carbohydrate (14.7%), nucleobase‐containing small molecule (15.6%), cellular amide (14.7%) and carbohydrate derivative biosynthetic process (12%) were the most representative biological processes of all identified enzymes. Neutrophil degranulation, carbon and amino acid metabolism were the main pathways respectively that these enzymes are involved.Conclusions: Open‐access proteomic studies enable the pooling of all detected proteins and enzymes to have a great quantity of data. OS harbours hundreds of enzymes, which are involved in the homeostasis and defence mechanisms of OS. Enzymes could be attractive targets for novel treatments in OS pathologies due to their druggability property.