Changes in Activity and Kinetic Properties of the Proteasome in Different Rat Organs during Development and Maturation

Table 3

Proteasome activity in rat lens.

Type of activity	Age	Mean ± SD	𝑃-value
(Substrate)		(RFU × s^-1× g^-1)
Chymotrypsin-like	newborn	0.23±0.14
activity (LLVY)	young/fertile	0.28±0.05	N.S.
	middle aged	0.30±0.04	N.S.
	old	0.36±0.11	.026*
Calcium-dependent	newborn	0.03±0.06
chymotrypsin-like activity	young/fertile	<0.00	N.A.
(LLVY w 1 mM Ca^2+	middle aged	<0.00	N.A.
- LLVY wo Ca^2+)	old	<0.00	N.A.
Trypsin-like activity	newborn	0.15±0.07
(VGR)	young/fertile	0.20±0.04	N.S.
	middle aged	0.24±0.03	N.S.
	old	0.37±0.10	<.001^*†,.030^‡
Peptidylglutamyl-	newborn	0.21±0.08
peptidase activity (LLE)	young/fertile	0.29±0.06	.040*
	middle aged	0.35±0.04	.013*
	old	0.40±0.09	<.001*,.008^†

Chymotrypsin-like, trypsin-like, and peptidylglutamyl-peptidase activities in the soluble fractions of rat lens homogenate from newborn (7 days, 𝑛=23), young (2–4 months, 𝑛=12), middle aged (10 months, 𝑛=4), and old (18–24 months, 𝑛=9) rats. Calcium-dependent chymotrypsin-like activity was defined as the net difference between proteolysis of LLVY with and without calcium, respectively. Proteolytic activity is expressed as relative fluorescence units (RFUs) per second and gram of protein. Mean ± SD (standard deviation) is shown. Statistical analysis was made using ANOVA with Bonferroni as post hoc. A 𝑃-value of less than  .05 was considered statistically significant. N.A. = Not Applicable; in these cases addition of calcium caused an inhibition of the activity, yielding a net negative calcium-dependent activity. N.S. = Not Significant. Significantly higher activity as compared to *newborn, ^†young and ^‡middle aged groups.