1.   The drugs work by blocking a key enzyme used by the human immunodeficiency virus in its reproductive cycle.

2.   The new results are from studies with protease inhibitors, drugs that block a key viral enzyme.

3.   The protease inhibitor blocks a key viral enzyme called protease, and the older drugs block a different enzyme.

4.   The third family is proteases, which work by blocking a key enzyme involved in viral diseases such as AIDS.

5.   They do so by reining in a key enzyme involved in inflammation, and they do it with more clout than does hydrocortisone.

6.   They make cholesterol levels plummet by blocking a key enzyme required in its synthesis.

7.   Writing in the journal Molecular Cell, researchers report that increased levels of manganese in yeast cells slow the activity of a key enzyme, reverse transcriptase.

8.   It works by blocking a key enzyme that makes hair grow and must be used regularly or else hair growth will resume.

9.   Last year, German researchers reported that the failure of a key enzyme to mop up dying cells also contributes to lupus.

10.   The drugs block a key enzyme used by the virus in its reproductive cycle, and raise the level of critical immune cells depleted by AIDS.