  We present a catalogue of X-ray luminosities for 401 early-type galaxies, of
which 136 are based on newly analysed ROSAT PSPC pointed observations. The
remaining luminosities are taken from the literature and converted to a common
energy band, spectral model and distance scale. Using this sample we fit the
L_X:L_B relation for early-type galaxies and find a best fit slope for the
catalogue of ~2.2. We demonstrate the influence of group-dominant galaxies on
the fit and present evidence that the relation is not well modeled by a single
powerlaw fit. We also derive estimates of the contribution to galaxy X-ray
luminosities from discrete sources and conclude that they provide
L_discrete/L_B = 29.5 erg/s/L_solar. We compare this result to luminosities
from our catalogue. Lastly, we examine the influence of environment on galaxy
X-ray luminosity and on the form of the L_X:L_B relation. We conclude that
although environment undoubtedly affects the X-ray properties of individual
galaxies, particularly those in the centres of groups and clusters, it does not
change the nature of whole populations.
