Mayor Gavin Newsom’s exploratory committee for the 2010 California governor’s race broke the $50,000 mark Wednesday with donations from the heads of two Bay Area investment firms.

Newsom collected checks totaling $20,000 from Marin County residents Carmel and Eric Greenberg, Democratic Party supporters and the president of Innovation Investments, according to the Secretary of State’s Web site.

Newsom also collected a check for $24,100 from Palo Alto-based investor Theodore Janus.

Newsom’s political advisor, Eric Jaye, said the 41-year-old mayor has received hundreds of smaller donations from supporters as well.

The exploratory committee must now file all donations over $1,000 electronically with the California Secretary of State as a result of breaking the $50,000 barrier.