Answer:

lysine

Answer	Crossword Clue
LYSINE	Amino acid
LYSINE	Important basic amino acid.
LYSINE	Important amino acid

LYSINE	Essential amino acid
LYSINE	Basic amino acid
LYSINE	An amino acid
LYSINE	Certain amino acid

Crossword

a puzzle consisting of a grid of squares and blanks into which words crossing vertically and horizontally are written according to clues.