SEATTLE - Shareholders of Enterprise Bank, Bellevue, Wash., voted  last week to approve its merger into Washington Mutual Bank of Seattle,   which is owned by the $20 billion-asset Washington Mutual Inc.   
The approval paved the way for completion of the transaction, which was  agreed to in early June, at the close of business last Thursday. 
  
Enterprise shareholders were to receive 0.57377 share of Washington  Mutual common stock for each Enterprise share, though the exchange ratio   could be altered slightly if the merger is not treated as a pooling of   interests.     
The $132 million-asset, single-branch Enterprise Bank brings Washington  Mutual a center of small-business expertise. The bank will operate as a   division of Washington Mutual, managed by Thomas E. Cleveland, Enterprise's   chairman and founder.