been reported (Izumi et al., 1990;

been reported (Izumi et al., 1990; Janssen et al., 1994; Gao and Breuil, 1995; Kim et al.,
1998; Lee et al., 1999). An extracellular Bacillus lipase isolated by Sidhu et al. (1998a,b) had an activity optimum at 50
C. The enzyme had a half-life of 15 min at 75
C and it was stable to various oxidizing, reducing, and chelating agents. The enzyme was stable in the presence of surfactants and in organic solvents (Sidhu et al., 1998a,b). The crude lipase had an activity of 8.2 U/mL at 50
C and pH 8.0. The activity was further enhanced by the presence of Ca2+ (Sidhu et al., 1998a,b). Thermal stability of porcine pancreatic lipase has been discussed by Kiran et al. (2001b). Thermal stability of a lipase is obviously related with its structure (Zhu et al., 2001). Thermostability is influenced by environmental factors such as pH and the presence of metal ions. At least in some cases, thermal denaturation appears to occur through intermediate states of unfolding of the polypeptide (Zhu et al., 2001). Mutations in the ‘lid’ region of the enzyme can significantly affect heat stability (Zhu et al., 2001). Attempts are being made to proteinengineer lipases for improved thermal stability. Compared to the native enzyme, thermal and operational stability of many lipases can be significantly enhanced by immobilization (Xu et al., 1995; Reetz et al., 1996; Arroyo et al., 1999; Hiol et al., 2000). C. antarctica lipase B could be thermally stabilized by immobilization (Arroyo et al., 1999). The native enzyme and the covalently immobilized preparation appeared to follow different modes of thermal deactivation (Arroyo et al., 1999).
6.1. Effect of metal ions and chelating agents on lipase activity
Chartrain et al. (1993) observed that an extracellular lipase of P. aeruginosa MB5001 was
strongly inhibited by 1 mM ZnSO (94% inhibition) but was stimulated by adding 10 mM CaCl
2 4 (1.24-fold stimulation) and 200 mM taurocholic acid (1.6-fold stimulation). Mase et al.
(1995) studied the effect of metal ions (1 mM concentration) on a purified lipase of Pe. roqueforti IAM7268. The lipase activity was not affected by Ca Na+ ,K+ ,Cu2+ ,Na 2+ , EDTA, p-chloro mercuribenzoic acid, and iodoacetate (Mase et al., 1995). In contrast, the enzyme was inhibited by Ag+ ,Fe2+ ,Hg 2+ , and isopropyl fluorophosphate. In another similar study with metal ions (1 mM) and chelating agents, P. pseudoalcaligenes F-111 lipase activity was 60% inhibited by Fe 3+ but not by Ca 2+ ,Hg+ ,Mg 2+ , Cu2+ ,Mg2+2+,Co2+ ,Cd ,and Pb2+ (Lin et al., 1996). Metal chelators (EDTA, o-phenanthrolin) did not significantly affect the alkaline lipase activity (Lin et al., 1996). Sharon et al. (1998) reported a lipase of P. aeruginosa KKA-5 that retained its activity in presence of Ca2+ and Mg 2+ but was slightly inhibited by Mn2+ ,Cd 2+ , and Ba 2+ ,Zn , and Cu . Salts of heavy metals (Fe 2+ ,Zn 2+ ,Hg2+ ,Fe3+ ) strongly inhibited the lipase, suggesting that they were able to alter the enzyme conformation (Sharon et al., 1998). The effect of various metal ions on S. epidermidis lipase activity was reported by Simons et al. (1998). The enzyme needed calcium as a cofactor for catalytic activity (Simons et al., 1998). Biochemical characterization showed that this lipase was closely related to the lipase of
S. aurelis NCTC 8530. Both the enzymes had a pH optimum of around 6.0 and were quite
stable at low pH. Hiol et al. (2000) studied the effect of various compounds and enzyme 2+ 2+
,Mn ,Mn 2+ 2+ 2+
,

Hasil (Bahasa Indonesia) 2:

dilaporkan (Izumi et al, 1990;.. Janssen et al, 1994; Gao dan Breuil, 1995; Kim et al,.
1998; Lee et al, 1999.). Sebuah Bacillus lipase ekstraseluler diisolasi oleh Sidhu et al. (1998a, b) memiliki optimum aktivitas pada 50? C. Enzim memiliki paruh 15 menit pada 75? C dan itu stabil untuk berbagai oksidasi, mengurangi, dan chelating agen. Enzim stabil dengan adanya surfaktan dan pelarut organik (Sidhu et al., 1998a, b). Lipase mentah memiliki aktivitas 8,2 U / mL pada 50? C dan pH 8,0. Kegiatan ini lebih ditingkatkan dengan adanya Ca2 + (Sidhu et al., 1998a, b). Stabilitas termal lipase pankreas babi telah dibahas oleh Kiran et al. (2001b). Stabilitas termal lipase yang jelas berkaitan dengan struktur (Zhu et al., 2001). Thermostability dipengaruhi oleh faktor lingkungan seperti pH dan kehadiran ion logam. Setidaknya dalam beberapa kasus, denaturasi termal tampaknya terjadi melalui negara-negara menengah terungkapnya polipeptida (Zhu et al., 2001). Mutasi di 'tutup' wilayah enzim dapat secara signifikan mempengaruhi stabilitas panas (Zhu et al., 2001). Upaya yang dilakukan untuk proteinengineer lipase untuk stabilitas termal ditingkatkan. Dibandingkan dengan enzim asli, stabilitas termal dan operasional banyak lipase dapat secara signifikan ditingkatkan dengan imobilisasi (Xu et al, 1995;.. Reetz et al, 1996;. Arroyo et al, 1999;. Hiol et al, 2000). C. antarctica lipase B dapat termal distabilkan oleh imobilisasi (Arroyo et al., 1999). Enzim asli dan persiapan kovalen bergerak tampaknya mengikuti berbagai mode penonaktifan termal (Arroyo et al., 1999).
6.1. Pengaruh ion logam dan agen chelating aktivitas lipase
CHARTRAIN et al. (1993) mengamati bahwa lipase ekstraselular P. aeruginosa MB5001 yang
sangat dihambat oleh 1 mM ZnSO (penghambatan 94%) tetapi dirangsang dengan menambahkan 10 mM CaCl
2 4 (stimulasi 1,24 kali lipat) dan 200 mM asam taurokolat (1,6 kali lipat stimulasi). Mase et al.
(1995) mempelajari pengaruh ion logam (1 konsentrasi mM) pada lipase dimurnikan dari Pe. roqueforti IAM7268. Kegiatan lipase tidak terpengaruh oleh Ca Na +, K +, Cu2 +, Na 2+, EDTA, p-chloro asam mercuribenzoic, dan iodoacetate (Mase et al., 1995). Sebaliknya, enzim ini dihambat oleh Ag +, Fe2 +, Hg 2+, dan isopropil fluorofosfat. Dalam penelitian lain yang serupa dengan ion logam (1 mM) dan agen chelating, P. pseudoalcaligenes aktivitas lipase F-111 adalah 60% dihambat oleh Fe 3+ tetapi tidak oleh Ca 2+, Hg +, Mg2 +, Cu2 +, Mg2 + 2 + , Co2 +, Cd, dan Pb2 + (Lin et al., 1996). Chelators logam (EDTA, o-fenantrolin) tidak secara signifikan mempengaruhi aktivitas lipase alkali (Lin et al., 1996). Sharon et al. (1998) melaporkan lipase dari P. aeruginosa KKA-5 yang mempertahankan aktivitasnya di hadapan Ca2 + dan Mg2 + tapi sedikit dihambat oleh Mn2 +, Cd 2+, dan Ba 2+, Zn, dan Cu. Garam logam berat (Fe 2+, Zn 2+, Hg2 +, Fe3 +) sangat menghambat lipase, menunjukkan bahwa mereka mampu mengubah konformasi enzim (Sharon et al., 1998). Pengaruh berbagai ion logam pada aktivitas lipase S. epidermidis dilaporkan oleh Simons et al. (1998). Enzim diperlukan kalsium sebagai kofaktor untuk aktivitas katalitik (Simons et al., 1998). Karakterisasi biokimia menunjukkan bahwa lipase ini erat kaitannya dengan lipase dari
S. aurelis NCTC 8530. Kedua enzim memiliki pH optimum sekitar 6,0 dan cukup
stabil pada pH rendah. Hiol et al. (2000) meneliti efek dari berbagai senyawa dan enzim 2+ 2+
, Mn, Mn 2+ 2+ 2+
,