title: A dopa decarboxylase modulating the immune response of scallop Chlamys farreri.
abstract: BACKGROUND
  Dopa decarboxylase (DDC) is a pyridoxal 5-phosphate (PLP)-dependent enzyme that catalyzes the decarboxylation of L-Dopa to dopamine, and involved in complex neuroendocrine-immune regulatory network. The function for DDC in the immunomodulation remains unclear in invertebrate.
  
  
  METHODS
  The full-length cDNA encoding DDC (designated CfDDC) was cloned from mollusc scallop Chlamys farreri. It contained an open reading frame encoding a polypeptide of 560 amino acids. The CfDDC mRNA transcripts could be detected in all the tested tissues, including the immune tissues haemocytes and hepatopancreas. After scallops were treated with LPS stimulation, the mRNA expression level of CfDDC in haemocytes increased significantly (5.5-fold, P<0.05) at 3 h and reached the peak at 12 h (9.8-fold, P<0.05), and then recovered to the baseline level. The recombinant protein of CfDDC (rCfDDC) was expressed in Escherichia coli BL21 (DE3)-Transetta, and 1 mg rCfDDC could catalyze the production of 1.651±0.22 ng dopamine within 1 h in vitro. When the haemocytes were incubated with rCfDDC-coated agarose beads, the haemocyte encapsulation to the beads was increased significantly from 70% at 6 h to 93% at 24 h in vitro in comparison with that in the control (23% at 6 h to 25% at 24 h), and the increased haemocyte encapsulation was repressed by the addition of rCfDDC antibody (which is acquired via immunization 6-week old rats with rCfDDC). After the injection of DDC inhibitor methyldopa, the ROS level in haemocytes of scallops was decreased significantly to 0.41-fold (P<0.05) of blank group at 12 h and 0.47-fold (P<0.05) at 24 h, respectively.
  
  
  CONCLUSIONS
  These results collectively suggested that CfDDC, as a homologue of DDC in scallop, modulated the immune responses such as haemocytes encapsulation as well as the ROS level through its catalytic activity, functioning as an indispensable immunomodulating enzyme in the neuroendocrine-immune regulatory network of mollusc.
authors.affiliation: Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China.
authors.forename: Zhi
authors.initials: Z
authors.lastname: Zhou
authors.forename: Jialong
authors.initials: J
authors.lastname: Yang
authors.forename: Lingling
authors.initials: L
authors.lastname: Wang
authors.forename: Huan
authors.initials: H
authors.lastname: Zhang
authors.forename: Yang
authors.initials: Y
authors.lastname: Gao
authors.forename: Xiaowei
authors.initials: X
authors.lastname: Shi
authors.forename: Mengqiang
authors.initials: M
authors.lastname: Wang
authors.forename: Pengfei
authors.initials: P
authors.lastname: Kong
authors.forename: Limei
authors.initials: L
authors.lastname: Qiu
authors.forename: Linsheng
authors.initials: L
authors.lastname: Song
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D017931:DNA Primers; D018076:DNA, Complementary; D004296:Dopa Decarboxylase / Q000235:genetics / Q000378:metabolism*; D020224:Expressed Sequence Tags; D008969:Molecular Sequence Data; D049897:Pectinidae / Q000276:immunology*; D016133:Polymerase Chain Reaction; D017382:Reactive Oxygen Species / Q000378:metabolism
chemical_list: D017931:DNA Primers; D018076:DNA, Complementary; D017382:Reactive Oxygen Species; D004296:Dopa Decarboxylase