  We present the optical light curve for the gamma-ray blazar PKS 1510-089 with
a significant variability of 2.0 mag within about 41 minutes in the R band
which is the most violently rapid variability detected in our optical
monitoring campaign operating since 1982. In the framework of the relativistic
beaming model, the central supermassive black hole mass of PKS 1510-089 is of
$(1.16-1.98)\times10^8M_\odot$. This is larger than some previous estimates for
the central mass in blazars that have been based on models for nonthermal
emission, but is consistent with the estimated result of the
$M_\bullet-\sigma_\star$ correlation. Some other physical parameters, including
the emission region size, Doppler factor $\delta$, the efficiency $\eta$ for
conversion of accreted matter into energy and luminosity are calculated. The
value of $\eta$ = 62.2 strongly implies that the relativistic beaming is
responsible for the rapid variability of the gamma-ray loud blazar PKS
1510-089.
