Before revision:  The identified protein structures showed that the main protease of COVID-19 virus is M^{pro which is a key CoV enzyme and an attractive drug target as it plays a pivotal role in mediating viral replication and transcription.
After revision:  The identified protein structures showed that the main protease of COVID-19 virus is or which is a key CoV enzyme and an attractive drug target as it plays a pivotal role in mediating viral replication and transcription.