Similarity in the sequence of a protein or nucleic acid or in the structure of an organ that reflects a common evolutionary origin. Molecules or sequences that exhibit homology are referred to as homologs. In contrast, analogy is a similarity in structure or function that does not reflect a common evolutionary origin.
An enzyme that phosphorylates (adds a phosphate group) to a substrate. The substrates for protein kinases are amino acids in other proteins, and they are divided into those specific for tyrosine and those specific for threonine/serine. Genes V, p.1245