  A universal quantum wave equation that yields Dirac, Klein-Gordon,
Schrodinger and quantum heat equations is derived. These equations are related
by complex transformation of space, time and mass. The new symmetry exhibited
by these equations is investigated. The universal quantum equation yields Dirac
equation in two ways: firstly by replacing the particle my $m_0$ by $im_0$, and
secondly by changing space and time coordinates by $it$ and $i\vec{r}$,
respectively.
