Abstract:A cytosolic manganese superoxide dismutase (cytMnSOD) gene and a mitochondrial manganese superoxide dismutase (mtMnSOD) gene were cloned from the kuruma shrimp Marsupenaeus japonicus using reverse transcription-polymerase chain reaction (RT-PCR) and rapid amplification of cDNA ends (RACE) method. The open reading frame (ORF) of cytMnSOD is 861 bp and encodes a 287 amino acids (aa) protein with a 61 aa leader sequence, whereas the ORF of mtMnSOD is 663 bp and encodes a 221 aa protein with a 21 aa mitochondrial-targeting sequence in the N-terminus. The calculated molecular mass of translated protein of cytMnSOD and mtMnSOD is 31.4 kDa and 24.3 kDa with an estimated pI of 5.62 and 7.27, respectively. The deduced amino acid sequence of cytMnSOD has similarity of 50.2% to that of mtMnSOD. Both cytMnSOD and mtMnSOD contain a manganese superoxide dismutase domain (DVWEHAYY), and four conserved amino acids responsible for binding manganese. Both cytMnSOD and mtMnSOD of M. japonicus were expressed in haemocytes, eyestalk, muscle, intestine, gill, and hepatopancreas. Both cytMnSOD and mtMnSOD transcripts in haemocytes of M. japonicus significantly increased 6 h after injection of Vibrio alginolyticus, and 12 h after injection of β-glucan, indicating induction of SOD system response in a short time.