I've never managed to get below 46 minutes for a 10k because there is actually quite a big fitness and training gap with just those two minutes. As Rhea points out it's down to miles per week and then raising the tempo from 4:36 km/minute to 4:30 (I think) or using another strategy such as increasing the tempo post 5k.
Increasing the weekly mileage will make shaving a few seconds per minute off easier, however the speed training is important for the races as you're rarely able to keep one consistent pace with a lot of runners.
I've linked it a few times on the site but the Runner's World Smart Coach can really help, and also doing the speed training on a treadmill. I realise that as someone who hasn't done a sub 45 minute race my advice is really just anecdotal, however I believe enough miles per week turns it into a breeze.