TABLE 4.

Effect of cysteine addition on the intracellular concentration of amino acids in strain 630Δerm

Amino acid	Amino acid concn (μmol/liter)		PYC/PY ratiob
	PY	PYC
Upregulated in presence of cysteine
Leucine	NDa	16.25 ± 1.6	+
Tyrosine	ND	20 ± 1.2	+
Alanine	13.5 ± 0.7	748 ± 40	55
Valine	5.3 ± 0.5	56.8 ± 1.3	10
Phenylalanine	2.6 ± 0.5	25.75 ± 5	10
Glutamic acid	19.3 ± 2	121.9 ± 9.5	6.5
Aminobutyric acid	8.5 ± 0.5	46.35 ± 0.8	5.5
Threonine	1.1 ± 0.1	2.4 ± 0.4	2.2
Serine	4 ± 0	9.85 ± 0.15	2.5
Asparagine	29.7 ± 2.6	59.7 ± 1.6	2
Methionine	4.85 ± 0.35	11.65 ± 1.65	2.5
Downregulated in presence of cysteine
Cystathionine	1.2 ± 0.2	ND	−
Glutamine	11.8 ± 0.4	6 ± 0.1	0.5
Hydroxyproline	23.3 ± 1.5	13.9 ± 0.5	0.6

^aND, not detectable.

^b+, detected only in PYC medium; −, detected only in PY medium.