The over expression of PQQ glucose dehydrogenase PQQGDH was investigated. The level of PQQGDH expressed in E. coli PP2418/pGEc1 was more than 10 fold when the cultivation was carried out under hole enzyme forming condition in the presence of 600 nM of PQQ and 10 mM of MgCl2, compared with those of apo condition. It may be due to the difference In thermal stability of apo and hole PQQGDH.