UPDATE 4-Portugal investigates firms co-owned by dos Santos; Angola may seek arrest warrant <!-- no image --> <div>* Portugal market regulator launches inquiries (Adds Isabel dos Santos' reaction, quote from Angola's finance minister at Davos)<div class="feedflare"> <a href="http://feeds.reuters.com/~ff/reuters/UKBankingFinancial?a=6eLFbu8GlR8:OYEfg28f5c8:yIl2AUoC8zA"><img src="http://feeds.feedburner.com/~ff/reuters/UKBankingFinancial?d=yIl2AUoC8zA" border="0"></a> <a href="http://feeds.reuters.com/~ff/reuters/UKBankingFinancial?a=6eLFbu8GlR8:OYEfg28f5c8:V_sGLiPBpWU"><img src="http://feeds.feedburner.com/~ff/reuters/UKBankingFinancial?i=6eLFbu8GlR8:OYEfg28f5c8:V_sGLiPBpWU" border="0"></a> <a href="http://feeds.reuters.com/~ff/reuters/UKBankingFinancial?a=6eLFbu8GlR8:OYEfg28f5c8:F7zBnMyn0Lo"><img src="http://feeds.feedburner.com/~ff/reuters/UKBankingFinancial?i=6eLFbu8GlR8:OYEfg28f5c8:F7zBnMyn0Lo" border="0"></a> </div><img src="http://feeds.feedburner.com/~r/reuters/UKBankingFinancial/~4/6eLFbu8GlR8" height="1" width="1" alt=""></div> Posted by Reuters