  The masses of $uudd\bar s $, $uudd\bar d$ and $uuss\bar d$ pentaquarks are
evaluated in a framework of both the Effective Hamiltonian approach to QCD and
spinless Salpeter using the Jaffe--Wilczek diquark approximation and the string
interaction for the diquark--diquark--antiquark system. The pentaquark masses
are found to be in the region above 2 GeV. That indicates that the Goldstone
boson exchange effects may play an important role in the light pentaquarks. The
same calculations yield the mass of $[ud]^2\bar c$ pentaquark $\sim$ 3250 MeV
and $[ud]^2\bar b$ pentaquark $\sim$ 6509 MeV.
