The protein telomerase helps maintain the protective caps at the ends of chromosomes which act like the ends of shoelaces and stop them unravelling.
As we age, and our cells divide, these caps become frayed and shorter and eventually are so damaged that the cell dies. Scientists believe boosting our natural levels of telomerase could rejuvenate them.
A team in Madrid tested the theory on mice and found that those genetically engineered to produce 10 times the normal levels of telomerase lived 50% longer than normal.
The enzyme was able to turn "a normal, mortal cell into an immortal cell".
The team was optimistic that a similar approach may eventually lead to extended human lifespans - though she urged caution.One of the problems with boosting telomerase is that it can increase the risk of cancer.
But this could be overcome by also using cancer drugs that could offset the negative affects.
The mice with the boosted enzyme also saw other health benefits - often associated with youth such as less subcutaneous fat and better glucose tolerance.